.  ,• 


l 

II 


, 


Refrigeration**^ 


y/  Practical  Treatise 

ON  THE  SCIENTIFIC  PRINCIPLES,   MECHANICAL  OPERATION,   AND  MANAGE- 
MENT   OF    REFRIGERATING    PLANTS    BASED    ON    THE    VARIOUS 
MODERN    SYSTEMS    OF    ARTIFICIAL    COOLING 


By  CHARLES  DICKERMAN 

Refrigerating  Engineer,  Pennsylvania  Iron  Works  Co. 

and 
FRANCIS  H.  BOYER 

Constructing  Engineer 


ILLUSTRATED 


CHICAGO 
AMERICAN  SCHOOL  OF  CORRESPONDENCE 

1909 


6ENERAL 


COPYRIGHT  1908  BY 
AMERICAN  SCHOOL  OF  CORRESPONDENCE 


Entered  at  Stationers'  Hall,  London 
All  Rights  Reserved 


Foreword 


recent  years,  such  marvelous  advances  have  been 
made  in  the  engineering  and  scientific  fields,  and 
so  rapid  has  been  the  evolution  of  mechanical  and 
constructive  processes  and  methods,  that  a  distinct 
need  has  been  created  for  a  series  of  practical 
working  guides,  of  convenient  size  and  low  cost,  embodying  the 
accumulated  results  of  experience  and  the  most  approved  modern 
practice  along  a  great  variety  of  lines.  To  fill  this  acknowledged 
need,  is  the  special  purpose  of  the  series  of  handbooks  to  which 
this  volume  belongs. 

C,  In  the  preparation  of  this  series,  it  has  been  the  aim  of  the  pub- 
lishers to  lay  special  stress  on  the  practical  side  of  each  subject, 
as  distinguished  from  mere  theoretical  or  academic  discussion. 
Each  volume  is  written  by  a  well-known  expert  of  acknowledged 
authority  in  his  special  line,  and  is  based  on  a  most  careful  study 
of  practical  needs  and  up-to-date  methods  as  developed  under  the 
conditions  of  actual  practice  in  the  field,  the  shop,  the  mill,  the 
power  house,  the  drafting  room,  the  engine  room,  etc. 

C,  These  volumes  are  especially  adapted  for  purposes  of  self- 
instruction  and  home  study.  The  utmost  care  has  been  used  to 
bring  the  treatment  of  each  subject  within  the  range  of  the  com- 

179722 


mon  understanding,  so  that  the  work  will  appeal  not  only  to  the 
technically  trained  expert,  but  also  to  the  beginner  and  the  self- 
taught  practical  man  who  wishes  to  keep  abreast  of  modern 
progress.  The  language  is  simple  and  clear;  heavy  technical  terms 
and  the  formulae  of  the  higher  mathematics  have  been  avoided, 
yet  without  sacrificing  any  of  'the  requirements  of  practical 
instruction;  the  arrangement  of  matter  is  such  as  to  carry  the 
reader  along  by  easy  steps  to  complete  mastery  of  each  subject; 
frequent  examples  for  practice  are  given,  to  enable  the  reader  to 
test  his  knowledge  and  make  it  a  permanent  possession;  and  the 
illustrations  are  selected  with  the  greatest  care  to  supplement  and 
make  clear  the  references  in  the  text. 

C.  The  method  adopted  in  the  preparation  of  these  volumes  is  that 
which  the  American  School  of  Correspondence  has  developed  and 
employed  so  successfully  for  many  years.  It  is  not  an  experiment, 
but  has  stood  the  severest  of  all  tests — that  of  practical  use — which 
has  demonstrated  it  to  be  the  best  method  yet  devised  'for  the 
education  of  the  busy  working  man. 

C,  For  purposes  of  ready  reference  and  timely  information  when 
needed,  it  is  believed  that  this  series  of  handbooks  will  be  found  to 
meet  every  requirement. 


Table    of    Contents 


PRINCIPLES  OF  REFRIGERATION,  AND  FREEZING  AGENTS         .       Page     3 

Unit  of  Refrigeration  (B.  T.  U.) — Specific  Heat — Latent  Heat — Units  of 
Plants — Thermometers  (Fahrenheit,  Reaumur,  Centigrade) — Freezing 
Agents  (Ammonia,  Carbonic  Acid,  Sulphur  Dioxide,  Compressed  Air) 


AMMONIA  COMPRESSION  SYSTEM    •  v.  s  .        .       .       .       .       Page     5 


Evaporators — Brine  Tank  (Rectangular  with  Flat  Coils,  Circular  with 
Spiral  Coils) — Washout  Opening — Bracing — Brine  Cooler  (Enclosed-Shell 
and  Double-Pipe  Types) — Compressors  (Single-Acting,  Double-Acting ;  Ver- 
tical, Horizontal) — Valves  (Inlet,  .  Discharge) — Piston — Stuffing-Box — 
Packing — Erection  of  Plant — Water-Jacket — Lubrication — bosses  and  their 
Avoidance — Ammonia  Condenser  (Submerged,  Atmospheric,  Double-Pipe)  — 
Water-Distributing  Devices — Slotted  Water  Pipe — Oil  Separator  or  .Inter- 
ceptor—Ammonia Receiver  or  Storage  Tank  (Vertical,  Horizontal) — Pipes 
and  Joints— Gasket  Fittings— Ells,  Tees,  Return  Bends — Valves  (Globe, 
Angle,  Gate;  Screwed  and  Flanged) — Pressure  Gauges  (Discharge  or  Con- 
densing Pressure,  and  Evaporator  or  Return-Gas  Pressure) — Brine 
(Chloride  of  Calcium,  Chloride  of  Sodium  or  Common  Salt) — Baume  Scale 
— Direct  Expansion  System— Baudelot  Cooler — Purging  and  Pumping  Out 
Connection — Testing  and  Charging — -Air-Pressure  Test — Vacuum  Test — 
Operation  and  Management  of  Plant — Prevention  of  Ammonia  Losses — 
Proportion  between  Parts  of  a  Refrigerating  Plant — Useful  Tables  (Ther- 
mometer Scales,  Properties  of  Saturated  Ammonia,  Properties  of  Calcium 
and  Salt  Brine 


CARBONIC  ANHYDRIDE,  COMPRESSED-AIR, 

AND  ABSORPTION  SYSTEMS       .       Page    81 


Refrigeration  by  Carbonic  Anhydride  Gas — Temperature  of  Liquefied  Gas — 
Refrigeration  by  Compressed  Air — Expansion  of  Air — Air-Compressor — Re- 
lief of  Valves — Unbalanced  Valve  Pressure — Oil  and  Water  Traps — Ice- 
Making  Tank— Refrigerator  Box— Water  "Butt"  or  Cooler — Ammonia  Ab- 
sorption System— Carre's  First  Ice  Plant — Reabsorbing — Circuit  of  Weak 
Water — Glass  Gauges — Gas  Foreign  to  Ammonia 


INDEX      .        .'     ,        .        ...        ,        ,        ,        .        ,        .        Page  107 


REFRIGERATION 

PART  I. 


Refrigeration  may  be  defined  as  the  process  of  cooling.  It  13 
artificially  or  mechanically  performed  by  transferring  the  heat 
contained  in  one  body  to  another,  thereby  producing  a  condition 
commonly  called  cold,  but  which  is  in  fact  an  absence  of  heat. 
This  transfer  of  heat  is  most  rapidly  and  economically  accomplished 
by  evaporation,  but  Defore  considering  the  apparatus  used  a  few 
important  definitions  sihould  be  reviewed. 

Unit  of  Refrigeration.  The  unit  or  basis  of  measurement 
of  refrigeration,  is  the  x.nit  of  heat,  and  in  the  United  States  and 
England  is  the  British  thermal  unit  (B.  T.  U.)  which  is  equiva- 
lent^to  raising  or  towering  tlie  temperature  of  one  pound  of  water 
1°  Fahrenheit  when  at  or  near  00°  Fahrenheit. 

Specific  Heat.  Specific  Heat,  or  capacity  for  heat,  is  the 
relative  capacity  of  a  substance  for  heat,  and  is  stated  or  expressed 
relative  to  that  of  water,  since  water  has  the  greatest  heat  capacity 
of  any  known  substance  except  Hydrogen. 

Latent  Heat.  "W  hen  a  body  changes  from  a  solid  to  a  liquid, 
or  a  liquid  to  a  gaseous  state,  a  certain  amount  of  heat  must  be 
supplied  to  it  in  order  to  effect  the  change.  This  amount  is  called 
its  latent  heat,  and  is  expressed  in  thermal  units.  Thus  we  have 
in  the  melting  of  one  pound  of  ice  a  latent  heat  of  142  thermal 
units,  and  we  understand  by  this  that  in  order  to  melt  a  pound  of 
ice  it  must  absorb  into  itself,  in  making  the  change,  142  B.  T.  U., 
or  the  equivalent  of  one  pound  of  water  changing  142  degrees 
Fahrenheit. 

Units  of  Machines  or  Plants.  The  unit  (or  capacity)  of 
refrigerating  plants  is  ordinarily  stated  in  tons,  that  is,  the  equiva- 
lent of  so  many  tons  of  ice  (of  2000  pounds)  at  32°  F  melted  into 
water  at  32°  F.  The  unit  is  equivalent  to  142x2000=284,000 
British  thermal  units. 

Thermometers.  For  ordinary  use,  a  mercury  tube  having  a 
graduated  surface  or  scale  at  its  back  with  a  bulb  at  its  lower  end 


REFKIGEKATION 


and  containing  a  quantity  of  mercury  is  used  to  denote  the  tem- 

ureiqlits  surroundings. 

c  Two  "different  scales  are  commonly  used  in  the  refrigerating 
:r  tfaev  Fahrenheit  and  Reaumer.  The  Centigrade  or 
French  standard  is  used  for  chemical  or  technical  purposes.  In 
the  United  States  and  England  the  Fahrenheit  scale  is  generally 
accepted  as  standard  except  in  breweries  where  the  German  or 
Reaumer  scale  is  quite  often  found. 

The  Fahrenheit  scale  is  divided  in  such  manner  that  the 
boiling  point  of  water  at  at- 
mospheric pressure  is  212° 
and  the  freezing  point  32°. 
It  is  said  that  0°  F  was  the 
lowest  temperature  Fahren- 
heit was  able  to  produce  by 
the  melting  of  ice  by  salt. 

The  Reaumer  scale  is  grad- 
uated by  making  the  boiling 
point  of  water  80°  while  the 
freezing  point  is  at  0°. 

The  Centigrade  has  the 
freezing  point  of  water  at  0° 
as  the  .Reaumer,  while  the 
boiling  point  is  fixed  at  100°. 
This  graduation  is  typical  of 
the  French  system  of  meas- 
urement. 

To  transpose  the  temperature  of  one  scale  to  that  of  the  others 
the  table  on  page  77  will  be  found  convenient. 

Let  us  now  take  an  illustration  from  a  branch  of  engineering 
with  which  almost  every  one  is  familiar. 

If  we  place  a  glass  of  water  in  contact  with  heat  at  a  temper- 
ature of  212°  F  or  more,  heat  will  pass  from  the  source  and  be 
absorbed  by  the  water  until  its  own  temperature  reaches  that  of 
212°,  after  which  evaporation  of  the  water  commences  and  con- 
tinues  until  the  water  has  all  been  transformed  into  steam.  During 
this  time  an  amount  of  heat  corresponding  to  this  duty  has  been 
transferred  from  the  source  of  heat  to  the  water  and  its  vapor 


Fig.  1. 


EEFEIGEEATION 


called  steam.  This  process  is  familiar  to  all  engineers,  in  the 
steam  boiler,  and  is  similar  to  that  of  refrigeration  as  ordinarily 
applied,  except  that  the  one  is  going  on  at  or  above  a  temperature 
of  212°  F  (the  boiling  point  of  water)  while  refrigeration  is  accom- 
plished by  the  evaporation  of  a  liquid  having  a  boiling  or  evapor- 
porating  point  sufficiently  low  to  obtain  the  desired  temperature. 

Agents.  Among  .the  most  commonly  used  agents  for  obtain- 
ing  artificial  refrigeration  may  be  mentioned  Ammonia,  Carbonic 
Acid,  Sulphur  Dioxide  and  Compressed  Air,  the  first  named  being 
the  most  generally  used  and  approved,  while  the  others  have 
advantages  for  use  on  ship-board  and  other  places  where  the  fumes 
of  ammonia  would  prove  objectionable.  Ammonia,  however, 
appears  to  present  the  most  favorable  qualities  for  general  use, 
and  will,  therefore,  be  the  principal  a'gent  considered. 


Fig.  2. 

Of  the  two  types  of  ammonia  machines,  the  absorption  and 
the  compression,  the  latter  will  be  the  first  described.  The  primi- 
tive process  of  refrigeration  is  represented  by  a  glass  or  receptacle 
(Fig.  1)  in  which  a  quantity  of  anhydrous  ammonia  is  placed,  and 
which,  so  long  as  its  own  temperature  and  that  of  its  surround- 
ings remain  at  or  above — 28°  F  or  28°  below  zero  (its  boiling 
.point)  will  continue  to  take  heat  over  to  itself,  and  therefore  con- 
tinue to  evaporate  and  produce  a  cooling  effect  upon  its  surround- 
ings, or  what  is  commonly  known  as  refrigeration  in  the  body  or 
substance  with  which  it  is  in  contact. 

In  Fig.  2  we  have  such  a  receptacle  to  which  is  attached  a 
drum  or  flask  filled  with  the  refrigerating  agent;  if  it  were  possi- 
ble to  procure  a  cheap  volatile  liquid,  having  a  sufficiently  low 


6 


EEFEIGEHATIOK 


CO 

bb 


KEFittGERATION 


boiling  or  evaporating  point,  the  complex  systems  of  refrigeration 
would  be  reduced  to  the  above  parts,  or  equivalent  simple  system. 
The  system  would  consist  of  an  evaporator,  and  a  receptacle  for 
the  refrigerant,  with  a  connecting  pipe  between,  provided  with  an 
expansion  valve  to  regulate  the  flow  of  the  liquid  to  the  evaporator. 
The  cost  of  ammonia  or  the  refrigerating  agent  renders  this  waste 
impracticable,  at  least  at  the  present  time;  and  to  make  refriger- 
ation  a  commercial  success  it  becomes  necessary  to  recover  and 
put  in  condition  to  be  used  again  the  gases  arising  from  the  evap. 
orating  ammonia.  We  have  seen  how  the  ammonia  absorbed  a 
certain  amount  of  heat  from  its  surroundings  during  evaporation; 
it  is  evident  that  this  heat  must  be  taken  from  it  before  it  can  be 
again  effective  as  a  refrigerant,  and  for  this  purpose  the  com« 
pressor,  condenser  and  other  adjuncts  to  the  plant  are  required. 

The  gas  pump  or  compressor  is  the  means  employed  to 
recover  and  compress  the  gas  from  the  evaporator.  In  order, 
therefore,  to  continue  the  process  of  refrigeration  in  a  commercial 
manner,  it  becomes  necessary  to  connect  to  the  evaporator  and 
ammonia  tank  shown  in  Fig.  2,  a  gas  pump  with  its  engine  or 
other  form  of  power.  This  is  illustrated  by  Fig.  3.  The  top  of 
the  evaporator  is  closed  and  provided  with  a  connecting  pipe  to 
the  compressor;  upon  the  downward  stroke  of  the  compressor 
piston  the  gas  from  the  evaporator  follows  and  fills  the  cylinder 
above  the  piston,  and  upon  reaching  the  bottom  of  its  stroke  this 
valve  is  closed  by  a  spring,  preventing  the  return  of  the  gas  to  the 
evaporator.  The  return  or  upward  stroke  of  the  piston  discharges 
the  gas  through  the  outlet  valve  and  pipe. 

Having  described  the  evaporation  of  the  ammonia  and  re- 
covery  of  its  gases  by  the  compressor,  we  now  supply  the  apparatus 
necessary  to  extract  the  heat  with  which  it  is  laden,  and  thereby 
cause  it  to  resume  its  initial  state  ready  to  again  enter  the  evapo- 
rator and  continue  the  cycle.  The  apparatus  referred  to  is  called 
the  Ammonia  Condenser.  Fig.  4  illustrates  its  construction  and 
connection  with  the  balance  of  the  apparatus. 

The  discharge  of  the  ammonia  gas  from  the  compressor  is 
continued  through  the  pipe  E,  the  oil  separator  F,  and  into  the 
condenser  C,  which  is  composed  of  a  series  of  pipes  over  which 
water  flows  to  take  up  the  heat  given  out  by  the  compressing  of 


8 


REFKIGEEATION 


the  gas.  and  which  combined  effect  pauses  the  gas  to  liquify  and 
flow  from  the  bottom  pipe  of  the  condenser  through  the  pipe  II  to 
the  receiver  or  storage  tank  I.  This  completes  the  cycle  and  per* 
forms  the  practical  process  of  refrigeration. 

The  principle  or  method  of  refrigeration  has  now  been  de- 


scribed without  going  into  details  of  construction.  The  next  step 
is  the  construction,  proportion  and  combination  of  the  several 
parts  making  up  the  refrigerating  plant,  and  as  the  evaporator  is 
the  foundation  or  basis  of  the  system,  let  us  first  consider  this 
part  of  the  plant. 

EVAPORATORS. 
Evaporators  may  be  divided  into  two  classes:     The  first  is 


15    TO    20    TON    REFRIGERATING    MACHINE. 

Frick  Company. 


EEFEIGEEATION 


9 


operated  in  connection  with  the  brine  system.  In  this  evaporator 
salt  brine  (or  other  solution)  is  reduced  in  temperature  by  the 
evaporation  of  the  ammonia  or  other  refrigerant  and  the  cooled 
brine  circulated  through  the  room  or  other  points  to  be  refriger- 
ated. In  the  second,  the  direct-expansion  system,  the  ammonia 
or  refrigerant  is  taken  directly  to  the  point  to  be  cooled,  and  there 
evaporated  in  pipes  or  other  receptacles,  in  direct  contact  with  the 
object  to  be  cooled.  Which  of  the  two  systems  is  better,  is  a  much 
disputed  and  debated  point;  we  can  state,  in  a  general  way,  that 


Fig.  5. 

both  have  their  advantages,  and  each  is  adapted  to  certain  classes  of 
duty. 

The  cooling  of  brine  in  a  tank  by  a  series  of  evaporating 
coils,  (one  of  the  earliest  methods)  is  common  to-day,  A  descrip- 
tion of  the  many  methods  of  construction  and  equipment  would 
require  much  space.  Let  us,  therefore,  discuss  the  two  most 
general  types  only,  viz:  the  rectangular  with  flat  coils,  and  the 
circular  with  spiral  coils. 

Fig.  5  shows  a  sectional  view  of  a  brine  tank.  Flat  or  zig- 
zag evaporating  coils  are  connected  to  manifolds  or  headers;  the 
pipe  connections  leading  to  and  from  these  manifolds  for  the 
proper  supplying  of  the  liquid  ammonia  and  the  taking  away  or 
return  of  the  gas  to  the  compressor  are  also  shown.  For  coils  of 


10  KEFKIGEKATION 

this  type,  1-inch  or  IJ-inch  pipe  is  preferable,  owing  to  the 
impossibility  of  bending  larger  sizes  to  a  small  enough  radius  to 
get  the  required  amount  into  a  tank  of  reasonable  dimensions.  It 
is  possible  to  make  coils  of  this  construction  of  any  desired  length 
or  number  of  pipes  to  the  coil,  "pipes  high,"  the  bends  being 
from  3J  inches  to  4  inches  centers  for  1-inch  pipe,  and  4  inches 
to  5  inches  for  l|-inch  pipe.  It  is  preferable  to  make  the  coils  of 
moderate  length,  (not  less  than  150  feet  in  each)  and  there  is  no 
disadvantage  (other  than  in  handling)  in  making  them  to  contain 
up  to  500  or  600  feet  each.  It  will  be  observed  that  there  is  a 
slight  downward  pitch  to  the  pipes  with  a  purge  valve  at  the  low- 
est point  of  the  bottom  manifold,  which  is,  undoubtedly,  valuable 
and  an  almost  necessary  provision.  This  valve  is  for  removing 
foreign  matter,  which  may  enter  the  pipes  at  any  time,  and  by 
opening  the  valve  and  drawing  a  portion  of  their  contents,  the 
condition  of  cleanliness  can  be  determined  without  the  necessity 
of  shutting  down  and  removing  the  brine  and  ammonia  for 
inspection.  The  coils  are  usually  strapped  or  bound  with  flat  bar 
iron  about  J  inch  X  2  inches  (or  a  little  heavier  for  the  longer 
coils)  and  bolted  together  with  -|-inch  square-head  machine  bolts. 
The  coils  are  painted  with  some  good  water-proof  or  iron  paint. 
The  brine  tank  is  usually  constructed  of  iron  or  steel  plates, 
varying  from  T3^-  inch  to  §  inch  in  thickness ;  the  average  being  ^ 
inch  for  tanks  of  ordinary  size.  The  workmanship  and  material 
for  a  tank  for  this  purpose  should  be  of  the  very  best;  without 
these  the  result  is  almost  certain  to  be  disastrous  to  the  owner  or 
builder.  The  general  opinion  with  iron  workers  (before  they  have 
had  experience)  is  that  it  is  a  simple  matter  to  make  a  tank  which 
will  hold  water  or  brine,  and  that  any  kind  of  seam  or  workman- 
ship will  be  good  enough  for  the  purpose.  On  the  contrary  the 
greatest  care  and  attention  to  detail  is  necessary.  It  is  customary, 
and  good  practice,  to  form  the  two  side  edges  at  the  bottom  by 
bending  the  sheets,  thereby  avoiding  seams  on  two  sides,  while 
for  the  ends  an  angle  iron  may  be  bent  to  conform  to  this  shape 
and  the  two  sheets  then  riveted  to  the  flanges  of  the  angle  iron. 
The  edges  of  the  sheets  should  be  sheared  or  planed  bevel,  and 
after  riveting,  calked  inside  and  out  with  a  round-nosed  calking 
tool.  The  rivets  should  be  of  full  size,  as  specified  for  boiler  con- 


EEFEIGERATION  11 


struction  and  of  length  sufficient  to  form  a  full  conical  head  of 
height  equal  to  the  diameter  of  the  rivet  and  brought  well  down 
onto  the  sheet  at  its  edges.  An  angle  iron  of  about  3  inches 
should  be  placed  around  the  top  edge,  and  riveted  to  the  side  at 
about  12-inch  centers. 

One  or  more  braces  (depending  on  the  depth)  should  extend 
around  the  tank  between  the  top  and  bottom,  to  prevent  bulging; 
without  these  it  would  be  impossible  to  make  the  tank  remain 
tight,  as  a  constant  strain  is  on  all  its  seams.  A  very  good  brace 
for  the  purpose  is  a  deck  beam.  Flat  bar  iron  placed  edge-wise 
against  the  tank  with  an  angle  iron  on  each  side  and  all  riveted 
through  and  to  the  side  of  the  tank  with  splice  plates  at  the 
corners  or  one  of  each  pair  long  enough  to  lap  over  the  other 
makes  a  good  brace;  heavy  T-iron  is  also  used  to  some  extent.  It 
is  usual  to  rivet  up  the  bottom  of  the  tank  and  a  short  distance  up 
the  sides,  then  test  by  filling  with  water;  if  tight  lower  to  its 
foundation  and  complete  the  riveting  and  calking.  It  may  then 
be  filled  with  water  and  tested  until  proven  absolutely  tight,  when 
it  may  be  painted  with  some  good  iron  paint;  it  is  now  ready  for 
its  equipment  of  coils  and  insulation. 

A  washout  opening  with  stop  valve  should  be  placed  in  the 
bottom  at  one  corner;  for  this  purpose  it  is  well  to  have  a  wrought 
iron  flange,  tapped  for  the  size  of  pipe  required  and  riveted  to  the 
outside  of  the  bottom.  If  the  brine  pump  can  be  located  at  this 
time,  it  is  well  to  have  a  similar  flange  for  the  suction  pipe  riveted 
to  the  side  or  bottom  of  the  tank,  as  a  bolted  flange  with  a  gasket 
is  never  as  durable  as  a  flange  put  on  in  this  manner. 

O      i 

Assuming  that  the  tank  is  now  absolutely  tight  and  painted, 
the  insulation  may  be  put  around  it,  the  insulated  base  or  founda- 
tion having  been  put  in  previous  to  the  arrival  of  the  tank.  The 
insulation  should  be  constructed  of  joists  2  inches  or  3  inches  X 
12  inches  on  edge  and  filled  in  with  any  good  insulating  material 
and  floored  over  with  two  thicknesses  tongued  and  grooved  floor- 
ing with  paper  between.  In  putting  the  insulation  on  the  sides 
and  ends  of  the  tank,  place  joists  3  inches  X  4  inches  resting  on 
the  projecting  edges  of  the  foundation  about  2  feet  apart.  The 
upper  ends  should  be  secured  to  the  angle  iron  at  the  top  of  the 
tank,  its  upper  flange  having  been  punched  with  |-inch  holes  18 


12  REFRIGERATION 


inches  to  24  inches  centers  and  to  which  it  is  well  to  bolt  a  plank, 
having  its  edge  project  the  required  distance  to  receive  the 
uprights.  Between  the  braces  around  the  tank  blockings  should 
be  fitted  to  secure  the  frame  work  at  the  middle,  as  the  height  of 
some  tanks  is  too  great  to  depend  on  the  support  at  top  and  bot- 
tom alone. 

After  the  frame  work  has  been  properly  formed  and  secured 
to  the  base  and  tank,  take  1-inch  flooring,  rough,  or  planed  on  one 
side,  and  board  up  on  the  outside  of  the  uprights,  filling  in  as  the 
work  progresses  with  the  insulating  material  which  may  be  any 
one  of  the  usual  materials,  granulated  cork  being  about  the  best, 
all  things  considered,  although  charcoal,  dry  shavings,  saw-dust, 
or  other  non-conductors  may  be  used  with  good  results.  When 
the  first  course  of  boards  is  in  place  it  is  well  to  tack  one  or  two 
thicknesses  of  good  insulating  paper  against  the  outer  surface, 
care  being  taken  that  the  joints  lap  well  and  that  bottoms  and 
corners  are  filled  and  turned  under  at  the  junction  with  the 
bottom  insulation.  It  is  then  in  shape  for  the  final  or  outer 
course  which  is  very  often  made  <jf  some  of  the  hard  woods  in 
2^-inch  or  3-inch  widths,  tongued,  grooved  and  beaded  and 
finished  off  with  a  base  board  at  the  bottom  and  moulding  at  the 
top,  and  given  a  hard  wood  finish  in  oil  or  varnish.  If  the  tank 
is  located  in  a  part  of  the  building  in  which  appearance  is  of  no 
importance,  the  outer  course  may  be  a  repetition  of  the  first, 
except  that  the  boards  are  put  on  vertically  instead  of  horizontally. 

It  is  well  to  make  the  top  of  the  tank  in  removable  sections 
to  facilitate  examination  or  cleaning;  for  this  purpose  make  a 
number  of  sections  about  2^  to  3  feet  wide  of  the  length  or  width 
of  the  tank,  using  joists  about  2  inches  X  6  inches  placed  on 
edge,  floored  over  top  and  bottom  and  filled  in  with  the  selected 

O     '  i 

insulating  material.  It  is  also  well  to  have  a  small  lid  at  one  end 
of  each  (preferably  over  the  headers  or  manifolds)  which  will 
allow  of  internal  examination  of  the  tank  to  ascertain  the  height 
or  strength  of  brine  without  removing  the  larger  sectionr  The 
tank  is  now  fully  equipped  and  ready  for  testing  and  filling  with 
brine. 

For  a  circular  tank  the  general  instructions  regarding  con- 
struction  and  insulation  may  apply  as  with  the  rectangular  tank 


KEFKIGERATIOtf 


13 


just  described;  therefore  only  its  special  features  will  be  consid- 
ered. If  the  tank  is  small  and  there  is  sufficient  head  room  above 
it  for  handling  the  coils  there  cannot  be  serious  objection  to  this 
type  as  its  cost  is  lower  than  that  of  the  rectangular  tank.  This 
is  often  an  important  item  in  a  small  installation,  but  when  the 
tank  is  of  considerable  size  and  the  coils  large  it  is  not  as  readily 


Fig.  6. 

handled  and  taken  care  of  as  the  other  type.  The  usual  construc- 
tion of  a  nest  of  coils  for  a  round  tank  is  to  bend  the  inside  coil 
to  as  small  a  circle  as  possible,  which,  if  it  be  of  1-inch  or  1^-inch 
pipe  may  be  G  to  8  inches.  Increase  each  successive  coil  enough 
to  pass  over  the  next  smaller  until  the  required  amount  of  pipe  is 
obtained.  The  ends  may  then  be  bent  up  or  out  and  joined  to 
headers  at  top  and  bottom  and  the  tank  insulated  in  the  manner 
previously  described;  it  is  then  ready  to  test  and  charge  with 
ammonia  and  brine.  Fig.  6  represents  an  evaporator  of  this  type. 


14 


REFRIGERATION 


Other  constructions  of  tanks  and  coils  are  too  numerous  to  de- 
scribe in  detail,  and  with  one  exception  may  be  properly  classed 
in  one  of  the  preceding  types.  The  one  exception  referred  to  is 
illustrated  in  Fig.  7.  It  is  quite  common  and  is  adopted  for 
large  pipe  and  is  often  called  oval,  although  not  of  that  shape, 
but  rather  a  combination  of  the  flat  and  circular  form.  It  has 
some  good  features;  it  allows  the  maximum  amount  of  pipe  in 
the  smallest  space  and  a  large  amount  of  pipe  in  a  single  coil. 
The  Brine  Cooler  at  present  is  a  popular  and  efficient  method 


Fig.  7. 

of  cooling  brine  for  general  purposes.  Owing  to  mechanical 
defects  and  the  impossibility  of  obtaining  a  brine  solution  which 
would  not  freeze,  it  was  abandoned  only  to  be  taken  up  again,  and 
with  the  aid  of  modern  ideas  and  better  material  it  has  become 
highly  successful.  Unlike  the  brine  tank  and  coil  method  of  refrig- 
eration, in  which  the  ammonia  is  evaporated  within  the  coils  while 
the  brine  surrounds  them,  the  brine  passes  through  a  series  of 
coils  and  the  ammonia  evaporates  within  a  wrought  or  cast  suell 
surrounding  the  coils.  Thus  the  action  is  reversed. 

Fig.  8  is  what  is  known  as  the  enclosed-shell  type  of  brine 
cooler,  A  representing  a  cast  or  wrought-iron  shell,  flanged  at  each 
end,  to  which  heads  are  bolted;  a  tongue  and  grooved  joint  be- 


KEFKIGEBATION 


15 


tween,  makes  the  closed  cylinder  gas  tight.  B  is  a  series  of  welded 
extra  strong  pipe  coils,  one  with- 
in the  other,  having  their  ends 
project  through  the  heads  and 
joined  to  headers  at  each  end 
with  proper  unions ;  a  stop  valve 
is  supplied  to  each  coil.  Lock 
nuts  or  glands  are  placed  around 
each  coil  at  its  opening  through 
the  heads  and  one  or  more  glass 
gauges  with  the  usual  gauge 
fittings  are  tapped  into  the  side 
of  the  shell  to  indicate  the 
amount  of  ammonia.  Liquid 
ammonia  is  fed  into  the  shell 
by  an  ordinary  expansion  or 
feed  valve  near  the  lower  end 
of  the  shell  at  C  and  the  gas 
taken  off  through  the  opening 
and  pipe  D  to  the  compressor. 
A  purge  valve  E  for  drawing 
off  impurities  is  placed  at  the 
lowest  point  in  the  bottom  head 
and  a  second  one  F  for  gas  or 
air  in  the  top  head. 

In  operation,  the  discharge 
pipe  from  the  brine  pump  is  con- 
nected to  the  top  header  or  man. 
ifold,  and  the  bottom  header  is 
connected  to  the  main  leading 
to  the  refrigeration  to  be  per- 
formed;  the  return  from  the 
cooling  system  is  generally 
brought  to  a  medium-sized  brine 
tank  without  coils  to  which  the 
suction  of  the  pump  is  con. 
nected,  thereby  completing  the 
brine  circuit.  The  heat  of  the  brine  passing  through  the  coils  in 
the  cooler  is  taken  up  by  the  ammonia  during  evaporation;  the 


Fig.  8. 


16 


EEFKIGEEATIOX 


REFKIGEKATIOE  17 


gas  is  taken  away  from  the  top  of  the  shell  to  the  compressor,  and 
discharged  to  the  condenser  and  into  the  receiver  to  be  re-used,  as 
with  the  system  illustrated  by  Fig.  4. 

The  advantages  of  thejmne  cooler  over  the  brine _tank_are 
due  to  two  features  of  construction.  The  brine  in  passing  through 
the  coils  is  divided  into  a  number  of  small  streams,  and  while 
flowing  rapidly  through  a  coil  of  considerable  length  is  churned 
to  such  an  extent  that  it  is  all  brought  in  contact  with  the  coil,  of 
which  the  outer  surface  is  exposed  to  the  temperature  of  the  evap- 
orating or  boiling  ammonia,  and  thereby  gives  up  its  heat  much 
more  rapidly  to  the  ammonia  than  in  the  brine  tank.  In  the 
brine  tank  there  is  a  large  body  of  brine  with  scarcely  any  move- 
ment; the  brine  immediately  in  contact  with  the  pipe  may  be  quite 
cold,  but  becomes  warmer  as  the  distance  from  the  pipe  increases. 

The  second  advantage  is  that  during  the  evaporation  of  the 
ammonia  a  violent  ebullition  is  taking  place,  and  if  this  is  confined 
within  the  pipe  coil  a  certain  amount  of  the  liquid  is  carried  for- 
ward by  the  escaping  gas,  and  the  evaporation  within  the  coil  is 
limited.  This  limit  is  reached  when  the  vapor  enters  the  com- 
pressor in  such  quantities  as  to  cause  too  great  an  expansion  in 
the  compressor,  or  when  it  becomes  difficult  to  keep  the  stuffing- 
box  tight,  while  in  the  brine  cooler  properly  constructed,  the  larger 
diameter  of  shell  allows  evaporation  to  take  place  place  up  to 
practically  the  theoretical  boiling  point  of  the  ammonia,  without 
the  liquid  being  carried  forward  through  the  gas  pipe  to  the  com- 
pressor. This  permits  a  much  higher  evaporating  pressure  or 
"back  pressure"  as  it  is  commonly  called,  than  with  the  brine  tank 
and  coils.  Also  the  concentrated  or  compact  shape  and  construc- 
tion of  the  cooler  allows  greater  economy  than  the  large  radiating 
surface  of  the  brine  tank.  The  sides  and  end  of  the  cooler  are  in- 
sulated by  some  one  of  the  usual  methods  and  very  often  lagged 
with  finished  hardwood  strips,  tongue,  grooved  and  beaded  and 
bound  with  finished  brass  or  nickel  plated  bands. 

Salt  brine  is  commonly  used  in  the  brine  tank  and  coil  form 
of  refrigerator,  but  it  is  unsafe  to  use  it  with  the  brine  cooler 
because  when  passing  through  the  coil  it  may  freeze  and  burst  the 
coil.  A  solution  of  chloride  of  calcium  is  commonly  used,  its 


18  KEFKIGEKATION 


freezing  point  being  54°  below  zero  Fahr.  while  salt  brine  is  prac- 
tically  0°  Fahr. 

The  second  form  of  brine  cooler  is  what  is  known  as  the 
double=pipe  type,  the  construction  of  which  is  illustrated  in  Fig.  9, 
In  this  type  one  pipe  is  within  another,  the  brine  being  discharged 
from  the  pump  into  one  or  more  pipes  at  A  and  issuing  at  B. 
This  connection  leads  from  the  main  to  the  point  to  be  refrigerated 
and  the  ammonia  is  expanded  or  fed  into  the  annular  space  between 
the  two  pipes,  and  takes  up  the  heat  of  the  brine  in  evaporating 
and  issuing  as  gas  from  the  opening  D  at  the  top  of  the  cooler 
From  thence  the  ammonia  passes  to  the  compressor  and  through 
the  cycle  of  compression,  condensation  and  return  to  the  liquid 
ammonia  receiver  as  before.  The  ammonia  evaporating  between 
the  two  pipes  will  naturally  absorb  as  much  heat  from  the  outside 
surface  as  from  the  inner  or  brine  if  allowed  to  do  so,  and  it  there- 
fore becomes  necessary  to  insulate  the  outside  of  this  from  exterior 
influences.  As  it  is  practically  impossible  to  cover  the  bends  and 
irregular  surfaces  it  becomes  necessary  to  build  an  insulated  room 
in  which  the  cooler  is  erected.  This  is  commonly  done,  but  some 
authorities  do  not  consider  it  the  most  practical  form.  The 
cooler  is  equipped  with  the  necessary  stands,  manifolds  and  stop 
valves  to  properly  control  the  action  of  any  one  section  when 
more  than  one  is  used. 

As  with  the  enclosed  brine  cooler,  previously  described,  chlo- 
ride of  calcium  brine  should  be  used,  as  there  exists  the  same  lia- 
bility to  freeze,  and  it  is  unsafe  to  operate  either  type  with  the 
ordinary  salt  solution.  These  two  types  of  brine  coolers  and  brine 
tanks  and  coils  are  the  usual  means  of  cooling  or  refrigerating 
brine. 

COMPRESSORS. 

The  next  step  in  the  process  is  the  recovering  of  the  evaporated . 
ammonia  and  its  return  in  liquid  form.  Compressors  may  be 
divided  into  two  principal  classes,  single  acting  and  double  acting; 
and  each  class  subdivided  into  vertical  and  horizontal.  They 
are  of  the  vertical  type  if  single  acting,  and  of  both  vertical  and 
horizontal  if  double  acting,  although  the  majority  of  the  double 
acting  are  of  the  horizontal  type.  Machines  may  also  be  classed 
according  to  the  form  of  driving.  The  engines  used  may  be  hori- 


KEFEIGEBATION  19 


zontal  or  vertical,  and  within  this  classification  comes  almost  any 
machine  of  modern  build. 

Fig.  10  illustrates  the  vertical  single-acting  type  of  com- 
pressor, two  in  number,  in  combination  with  and  driven  by  a 
horizontal  Corliss  engine.  It  embodies  the  necessary  and  usual 
requisites  of  an  efficient  gas  pump  or  compressor. 

As  already  stated,  the  function  of  the  compressor  is  to 
recover  the  gas  from  the  evaporator  and  compress  it  into  the  con- 
denser at  a  pressure  which  will  cause  it  to  liquify  under  the 
action  of  the  cooling;  water.  It  is  evident  that  the  gas  must 

o  o 

follow  the  piston  in  its  downward  stroke  and  fill  the  compressor, 
and  upon  its  reaching  the  end  of  its  stroke  and  the  pressure  being 
balanced,  the  strength  of  the  spring  in  the  suction  valve  causes  it 
to  close  and  the  piston  begips  its  return  stroke.  The  compression 
of  the  gas  within  the  compressor  takes  place  until  its  pressure 
equals  or  slightly  exceeds  that  above  the  discharge  valve;  it  then 
opens  and  the  compressed  gas  flows  into  the  discharge  pipe 
and  thence  to  the  condenser.  Two  compressors  of  the  single- 
acting  type  are  almost  always  used  in  a  machine  of  this  type,  and 
the  cranks  set  opposite,  or  at  90°  to  one  another,  so  that  one  com- 
pressor is  filling  and  one  compressing  and  discharging  at  each  half 
revolution  of  the  crank  shaft,  and  the  load  is  accordingly  divided 
into  two  units,  either  one  of  which  may  be  operated  independently 
if  necessary. 

As  the  evaporator  is  the  heart  of  the  refrigerating  system,  so 
the  piston  and  valves  are  the  heart  of  the  compressor,  and  the 
principal,  almost  the  only,  cause  of  difficulty  in  the  action  of  the 
compressor  will  be  found  to  be  in  one  of  the  two. 

In  the  compressor  in  which  the  valves  operate  in  a  cage, 
there  must  of  necessity  be  a  gas-tight  joint  between  the  bottom  of 
this  cage  and  the  compressor  head  or  piston  in  which  it  is  located* 
this  joint  is  made  in  a  variety  of  ways,  any  one  of  which  will 
prove  effective.  A  square  shoulder  is  cut  into  the  head  with  a 
corresponding  shoulder  on  the  cage  to  match,  and  a  lead  gasket 
about  -£6  to  J  inch  in  thickness  placed  between  the  two.  Thia 
makes  a  durable  joint,  except  in  cases  where  the  joint  between 
the  two  is  of  such  an  amount  that  the  lead  is  constantly  pressed 
through  (a  disadvantage  of  lead  as  a  gasket  material).  "Without 


20 


KEFKIGEKATION 


EEFEIGEKATION 


one's  being  aware  of  the  fact,  tlie  gasket  is  gone  and  a  leakage 
exists.  Another  objection  to  a  lead  gasket  is  that  it  compresses 
and  knits  into  the  interstices  between  the  cage  and  the  head. 
This  often  makes  it  impossible  to  remove  the  valve  or  cage  from 
the  head  without  the  aid  of  some  kind  of  a  chain  block  or  tackle. 
Another  form  of  gasket  for  this  purpose,  but  not  popular  from  a 
lack  of  confidence  in  its  permanency,  is  common  lamp  or  candle 
wicking  saturated  with  oil  and  wound  tightly  and  smoothly  in 
the  corner  against  the  shoulder  on  the  cage.  It  is  put  in  place 
and  fully  compressed  by  pulling  down  on  the  valve  cap  until  the 
cage  is  at  the  desired  height.  It  is  good  practice  to  wind  enough 
on  until,  when  the  cage  is  pressed  down  by  hand,  it  stands  about 
fa  inch  above  the  surface  of  the  head  at  the  top;  this  amount  of 
compression  would  make  it  about  even  when  pulled  down.  As 
already  stated,  this  kind  of  packing  is  not  very  popular  on  ac- 
count of  lack  of  durability,  but  it  gives  very  satisfactory  results 
when  properly  applied,  and  the  valve  and  cage  may  be  easily 
removed.  Recently  the  gasket  has  been  omitted  and  a  ground 
joint  made  between  the  cage  and  the  head.  Although  its  efficiency 
has  not  yet  been  proven,  from  present  indications  it  should  be  both 
satisfactory  and  permanent. 

Assuming  that  we  have  made  the  joint  between  the  cage  and 
the  compressor  head  gas-tight,  we  must  also  be  certain  that  the 
compressor  valve  forms  a  perfect  joint  in  closing  against  the  cage. 
In  a  vertical  compressor,  in  which  the  action  of  the  valves  is  also 
vertical  within  their  cages,  the  conditions  naturally  favor  this  to 
the  greatest  possible  extent,  as  in  closing  they  drop  to  their  seats 
and  it  is  only  necessary  to  provide  for  the  slight  wear  taking  place 
in  the  stems  and  on  the  seats  due  to  the  rapid  opening  and  closing 
of  the  valves.  The  valve  stem  must  necessarily  fit  the  guides  in 
the  cage  as  closely  as  possible  and  still  allow  free  movement,  and 
the  seat  between  the  valve  disc  and  cage  (preferably  made  at  an 
angle  of  45°)  must  first  be  machined  to  the  proper  angle  and  then 
ground  in  the  usual  manner.  Having  made  it  impossible  for  the 
gas  to  pass  the  valves  and  cages,  means  must  be  provided  for 
closing  the  valves  at  the  proper  time  to  prevent  loss,  as  a  valve 
which  is  slow  in  reaching  its  seat  presents  a  double  evil — loss  of 
efficiency  and  improper  or  irregular  action  on  the  balance  of  the 


22  REFRIGERATION 


machine.  The  spring  is  the  usual  means  of  opening  the  com- 
pressor valve,  and,  on  the  suction  or  inlet,  is  commonly  placed 
between  the  top  of  the  cage  and  underneath  a  washer  placed  at 
the  end  of  the  stem  and  held  in  place  with  one  or  two  nuts;  it  is 
frequently  reinforced  with  a  buffer  spring,  or  one  of  greater 
strength,  enough  shorter  than  the  length  of  the  stems  to  allow  its 
opening  the  proper  distance,  and  then  stopping  the  travel  of  the 
valve  gently. 

Valves.  Fig.  11  illustrates  a  type  of  _inlet  valve  which  has 
stood  the  test  for  years  and  embodies  many  good  qualities.  The 
different  points  referred  to  are  indicated  by  the  following  letters: 
A,  the  joint  between  the  cage  and  head;  B,  the  contact  between 
the  valve  disc  and  the  cage;  C,  the  spring  for  actuating  the  valve, 
and  D,  the  buffer  or  stop  spring  to  stop  the  travel  of  the  valve  at 
the  proper  point  of  opening.  In  the  use  of  this  valve  the  require- 
ments are  that  it  shall  admit  the  gas  to  the  compressor  during  the 
downward  stroke  of  the  piston,  and  close  while  the  piston  is  at  the 
bottom  of  stroke  and  the  crank  pin  is  passing  the  bottom  center. 
It  will,  therefore,  be  readily  understood  that  if  the  spring  is 
stronger  than  necessary,  it  will  require  a  certain  amount  of  the 
pressure  of  the  gas  to  overcome  the  strength  of  the  spring,  and 
prevent  the  filling  of  the  compressor  to  its  fullest  limit.  In  the 
closing  of  the  valve  it  would  be  driven  with  considerable  force 
against  its  seat,  making  a  noise  in  so  doing  and  causing  excessive 
wear.  Considerable  skill  and  experience  are  required  to  obtain 
perfect  results,  but  with  good  judgment  and  a  few  trials  most  of 
the  imperfections  can  be  overcome.  Generally  the  closing  spring 
should  not  be  stronger  than  is  necessary  to  close  the  valve  when 
held  vertically  in  the  position  in  which  it  naturally  rests.  By 
taking  the  valve  and  cages  in  the  hands  and  pressing  down  on  the 
top  of  the  stem  with  one  of  the  fingers,  it  will  be  readily  ascer- 
tained when  the  springs  are  of  proper  strength  to  close  the  valve. 
When  put  on  the  compressor,  so  far  as  the  operation  of  the  inlet 
valves  is  concerned,  the  machine  will  be  practically  noiseless  and 
effective  in  the  admission  and  retention  of  the  gas  from  that  side. 

o 

The  discharge  valve  operates  in  the  reverse  direction  to  that 
of  the  suction  valve.  We  know  that  the  suction  valve  closes 
while  the  compressor  piston  is  at  its  lowest  position  in  the  com. 


BEFRIGERATIOH 


pressor  and  while  the  crank  is  passing  its  bottom  center.  The 
piston  now  moves  upward  compressing  the  gas  until  it  reaches  the 
pressure  in  the  ammonia  condenser,  and  as  it  passes  this  point  far 
enough  to  overcome  the  tension  of  the  spring  on  the  discharge 
valve,  it  causes  it  to  lift  and  the  contents  of  the  cylinder  in  its 
compressed  state  are  discharged  through  the  discharge  pipe  into  the 
condenser.  This  continues  until  the  piston  reaches  its  highest 


Fig.  11. 


point  and  the  crank  is  passing  its  top  center,  at  which  point  the 
valve  closes  and  the  suction  valve  again  opens  to  admit  an 
additional  amount  of  the  gas.  This  process  is  continued  during 
the  operation,  of  the  apparatus. 

It  will  be  noticed  that  the  suction  valve  opens  and  closes 
while  the  piston  is  practically  without  motion,  but  the  discharge 
valve  opens  while  the  piston  is  nearly  at  its  maximum,  and 
closes  while  the  piston  is  at  tne  minimum  speed.  From  this 
it  will  be  apparent  that  the  thrust  or  effort  on  the  discharge  valve 
is  much  greater  than  on  the  inlet,  that  is,  in  an  upward  or  out- 


BEFKIGEKATIOtf 


ward  direction ;  hence  the  device  for  arresting  the  upward  motion 
of  the  valve  must  be  more  effective  than  the  other.  Also  the 
valve  must  close  in  a  shorter  space  of  time  because  the  great 
pressure  above  the  valve  would  cause  it  to  fall  with  considerable 
force  were  it  not  to  reach  its  seat  while  the  piston  was  still  at  the 
top  of  its  travel,  and  the  pressure  above  and  below  equal.  Should 
the  piston  begin  its  return  or  downward  stroke  before  the  valve 
closes  it  would  have  the  condensing  pressure  above,  and  the  inlet 
pressure  below,  a  difference  of  from  150  to  175  pounds.  This 
pressure  would  cause  it  to  seat  with  an  excessive  blow  which 
would  soon  cause  its  destruction,  and  also  cause  the  escape  of  a 
portion  of  the  compressed  gas  into  the  compressor  resuming  in 
great  loss  in  efficiency  of  the  machine. 

To  stop  the  valve  in  its  opening  and  prevent  shock,  it  is  nee- 
essa/y  to  provide  a  buffer  or  cushion  -in  addition  to  the  spring 
used  to  close  it.  The  cushion,  as  usually  constructed,  is  a  piston 
fitting  closely  in  a  cylinder  and  provided  with  openings  for  the 
escape  of  the  gas  in  front  of  the  piston  until  it  reaches  a  certain 
height,  which  should  conform  to  the  lift  of  the  valve ;  at  this  point 
the  pisto'n  is  prevented  from  traveling  farther  by  the  compression 
of  the  gas  and  the  valve  is  brought  to  a  stop  without  noise  or  jar. 

The  strength  of  spring  for  closing  the  discharge  valve  must 
be  nicely  gauged;  if  too  light  the  valve  will  not  be  brought  to  its 
seat  until  the  piston  has  started  on  the  return  stroke,  causing  a 
return  to  the  compressor  of  a  portion  of  the  compressed  gas,  and 
the  striking  on  the  seat  writh  considerable  force  due  to  the  pres- 
sure of  the  gas  above  the  valve  and  the  removal  of  the  pressure 
below ;  while  if  the  spring  is  too  strong  the  valve  is  returned  with 
such  force  as  to  cause  a  harsh  sound  and  rapid  wearing.  This 
necessitates  more  frequent  renewals  than  if  moved  with  a  spring 
of  the  proper  tension. 

Inasmuch  as  the  weight  of  the  moving  part  of  the  valve  is  a 
factor  in  determining  the  required  strength,  and  the  diameter, 
pitch,  temper,  gauge  of  spring  and  material,  determine  the  strength, 
it  becomes  practically  impossible  to  lay  down  a  rule  for  the  selec- 
tion of  the  proper  spring  for  each  condition.  Experience  shows 
that  one  can  better  determine  what  spring  to  use  by  the  sense  of 
feeling  than  by  any  rule  or  standard" 


^JWtAR^ 

OP  THE 

UNIVERSITY 

Of 


REFRIGERATION  25 


Piston.  Having  provided  the  inlet  and  outlet  valves  with 
proper  opening  and  closing  devices  and  made  them  capable  of  retain- 
ing the  gas  passing  them,  a  piston  for  compressing  the  gas  and 
discharging  it  from  the  compressor  must  be  provided.  For  the 
vertical  type  of  single-acting  compressor  in  which  both  inlet  valves 
are  in  the  upper  compressor  head,  the  piston  is  best  made  as  a 
ribbed  disc  with  a  hub  at  the  center  for  the  piston  rod  and  a  peri- 
phery of  sufficient  width  to  be  grooved  for  the  necessary  snap 
rings.  Three  to  five  of  these  rings  are  generally  used. 

Fig.  12  illustrates  the  simplest  form  of  piston  of  this  type, 
A  being  the  cast  head,  B  the  snap  rings,  and  0  the  piston 
rod.  The  surface  is  faced  square  with  the  bore  of  the  hub,  and 


Pig.  12. 

the  rod  forced  in  and  riveted  over,  filling  the  small  counterbore 
provided  for  this  purpose.  The  cast  head  and  rod  having  been 
previously  roughed  out,  is  now  finished  in  its  assembled  condi- 
tion, the  rod  made  parallel  and  true  to  gauge,  threaded  to  fit  the 
crosshead  and  the  grooves  turned  for  the  snap  rings,  which  are 
made  slightly  larger  than  the  bore  of  the  compressor.  A  diagonal 
cut  is  made  through  one  side  and  enough  of  the  ring  is  cut  out  to 
allow  it  to  slip  into  the  cylinder  without  binding.  It  is  then 
scraped  on  its  sides  until  it  fits  accurately  the  groove  in  the  piston. 
It  is  also  well  to  turn  a  small  half-round  oil  groove  in  the  outer 
face  of  the  piston  between  each  ring  which  gathers  and  retains  a 
portion  of  the  oil  used  for  lubrication,  thus  increasing  the  efficiency 


26  EEFEIGEKATION 


of  the  piston  and  collecting  dust  or  scale  and  lessening  the  liability 
of  cutting  of  the  cylinder  due  to  any  of  the  usual  causes. 

The  piston  rod  requires  special  care  both  in  workmanship  and 
material.  In  order  to  be  effective  it  must  be  true  from  end  to 
end  and  to  be  lasting  under  the  variety  of  conditions  which  it 
operates,  should  be  of  a  good  grade  of  tool  steel.  The  end  which 
is  usually  made  to  screw  into  the  crosshead  is  turned  somewhat 
smaller,  usually  from  J  to  J  inch  in  diameter,  than  the  portion  pass- 
ing through  the  packing  or  stuffing  box  principally  to  allow  of 
returning  or  truing  up  the  rod  when  it  becomes  worn,  and  also  to 
allow  it  to  pass  through  the  stuffing  box.  After  the  rod  is  screwed 
into  the  crosshead  it  is  secured  and  locked  with  a  nut  to  prevent 
turning.  The  nut  also  allows  the  position  of  the  piston  to  be 
changed  to  compensate  for  wear  on  the  different  parts  of  the 
machine  by  simply  loosening  the  lock  nut  and  turning  the  piston 
and  rod  in  or  out  of  the  crosshead. 

The  stuffing  box  of  the  compressor,  shown  in  Fig.  13,  is  one 
of  the  most  difficult  parts  to  keep  in  proper  order.  This  is 
owing  principally  to  one  of  two  causes:  not  being  in  line  with 
the  crosshead  guide  or  bore  of  the  compressor,  or  the  great  dif- 
ference of  temperature  to  which  it  is  subjected  owing  to  the 
possible  changes  taking  place  in  the  evaporator.  However,  wTith 
the  compressor  crosshead  guides,  and  stuffing  box  in  perfect 
alignment,  and  a  constant  pressure  or  temperature  on  the  evap- 
orating side,  it  is  a  simple  matter  with  almost  any  kind  of 
packing  on  a  machine  of  the  vertical  single-acting  type  to  keep 
the  stuffing  box  tight  and  in  perfect  condition.  If,  however, 
either  of  the  above  conditions  are  changed  it  becomes  practically 
impossible  to  accomplish  this.  We  have  learned  that  perfectly 
constructed  and  operating  valves  is  one  of  the  essential  features  of 
a  perfect  machine.  We  also  know  that  the  alignment  of  the 
machine  is  equally  important. 

Erection.  Experience  in  the  building,  erecting  and  operation 
of  this  class  of  machinery,  shows  that  more  machinery  is  con- 
demned, more  complaints  made  and  difficulties  encountered  owing 
to  these  two  points  than  all  others  put  together.  It  is  all  im- 
portant to  the  erecting  and  operating  engineer  that  they  be 
absolutely  certain  of  these  two  points. 


REFRIGERATION 


After  the  A  frame,  the  compressor  cylinder  and  its  lower 
head  have  been  placed  in  position,  a  fine  hard  line  should  be 
passed  through  the  cylinder  and  stuffing  box  down  through  the 
guide  and  to  the  crank  pin  in  the  shaft,  drawn  tight  and  secured 
in  some  manner  at  each  end  and  then  callipered  at  each  point. 
The  different  parts  should  be  brought  into  perfect  alignment 
before  the  rest  of  the  machine  is  assembled. 

Fig,    14   illustrates    the    methods    of   obtaining   the   proper 


Fig.  13. 

results.  Assuming  that  the  brasses  are  central  with  the  connect- 
ing rod  and  the  connecting  rod  with  the  crossliead,  the  line  should 
of  course  be  central  with  the  crank  pin  and  this  condition  should 
exist  when  the  pin  is  at  its  top  and  bottom  positions.  In  other 
words,  when  the  line  is  placed  midway  between  the  collars  on  the 
crank  pin  when  at  the  bottom  stroke,  and  the  shaft  is  revolved 
one-half  revolution  to  its  top  stroke,  the  line  should  be  exactly 
midway  between  them;  or  the  top  moved  until  such  is  the  case, 
and  this  should  be  determined  as  absolutely  correct  before  pro- 
ceeding further.  When  this  is  accomplished  we  may  proceed  to 
the  guides  and  caliper  first  at  the  bottom  and  then  the  top 
between  the  line  and  each  side  of  the  bore,  moving  the  A  frame 
by  dressing  the  bottoms  of  the  feet  or  packing  under,  as  may  be 
most  desirable,- 


28 


REFRIGERATION 


We  may  now  examine  the  top  of  the  compressor  and  the 
bottom  of  the  stuffing  box  to  determine  whether  or  not  these  are 
central.  By  shimming  or  packing  under  the  side  of  the  com- 
pressor, the  cylinder  and  the  stuffing  box  may  be  moved  in  the 


required  direction;   this  will  be  found  all  that  is  necessary  to 

correct  the  small  inaccuracies.     Of  course,  should  objection  be 

raised  to  the  method,  the  other  remedy  is  to  dress  the  surfaces. 

Having  the  different  parts  in  proper  alignment,  we  may  now 


REFKIGEKATIOff  29 


proceed  with  the  assembling  of  the  balance  of  the  machine,  feeL 
ing  assured  that  with  reasonably  good  workmanship  and  material, 
we  will  have  a  good  running  machine.  It  is  well  to  have  a  com- 
pressor stuffing  box  of  any  of  the  several  types  in  two  parts  or 
double  packed  (see  Fig.  13),  the  inner  to  be  of  proper  proportion 
to  hold  the  packing  against  the  loss  of  ammonia  and  the  outer  of 
only  slight  depth  to  retain  the  lubricating  oil  within  the  annular 
space  provided  between  the  two,  and  through  which  the  rod  passes 
in  its  travel.  The  packing  may  be  drawn  up  or  tightened  by  any 
one  of  several  common  devices,  although  a  parallel  device  or  one 
which  causes  the  gland  to  move  uniformly  by  tightening  at  one 
point  is  to  be  preferred.  Although  three  or  four  separate  bolts 
are  very  often  used  they  are  undesirable  from  the  fact  that  they 
may  cause  a  tipping  or  "cocking"  due  to  the  tightening  or 
loosening  of  one. 

There  are  innumerable  materials  for  packing,  and  the  "  pack- 
ing  man  "  is  encountered  every  day  extolling  the  "good  qualities" 
of  his  packing.  It  is  probable  that  all  have  good  points,  but  it  is 
doubtful  if  any  one  make  or  kind  would  meet  with  the  unqualified 
indorsement  of  all  engineers;  also  no  one  packing  is  best  for  all 
conditions  or  duties.  The  condition  and  packing  must  be  suited  to 
one  another;  this  will  generally  be  accomplished  by  the  good 
engineer. 

In  the  construction  of  the  stuffing  box  it  is  well  to  bush  the 
bottom  of  the  glands  with  Babbitt  metal,  because  the  rod  is  often 
pressed  to  one  side  crowding  it  against  the  side  of  the  gland 
or  bottom  of  box,  causing  the  same  to  cut.  When  it  becomes 
necessary  to  turn  down  the  rod,  a  new  bushing  is  all  that  is  nee- 
essary  to  reduce  the  openings  correspondingly. 

Water  Jacket.  In  the  vertical  single-acting  type  of  com- 
pressor,  it  is  usual  to  provide  a  water  jacket,  which  may  be  cast 
in  combination  with  the  compressor  cylinder  or  made  of  some 
sheet  metal  secured  to  an  angle,  which  is  bolted  to  a  flange  cast 
on  the  cylinder.  It  is  usual  to  have  this  water  jacket  start  at 
about  the  middle  of  the  compressor  (or  a  little  below  as  shown 
in  Fig.  15)  and  extend  enough  above  to  cover  the  compressor 
heads,  valves  and  bonnets  with  water;  the  principal  object  of 
Which  is  to  keep  these  parts  at  a  normal  temperature  and  thereby 


30 


BEFEIGEKATIOK 


improve  the  operation  as  well  as  protect  the  joints  against  the 
excessive  heat  which  would  be  generated  by  the  continued  com- 
pression. It  is  also  an  advantage  in  the  operation  of  the  plant, 
since  by  reducing  the  temperature  in  the  compressor  and  adjacent 
parts,  the  compressor  is  filled  with  gas  of  a  greater  density.  It  is 
also  true  that  the  heat  extracted  or  taken  up  by  the  water  at 
this  point  is  a  certain  portion  of  the  worK  performed  in  the  con- 
denser  and  therefore  not  a  waste. 

In  the  operation  of  the  plant  it  is  well  to  have  plenty  of 
water  flow  through  the  jackets,  as 
the  cooler  the  compressors  are  kept 
the  better,  but  in  plants  in  which 
water  is  scarce  the  quantity  may  be 
reduced  correspondingly  until  the 
overflow  is  upwards  of  100°  Fahr. 
In  extreme  cases  of  shortage  of  water 
the  overflow  water  from  the  ammonia 
condenser  is  sometimes  used  on  the 
water  jackets,  that  is,  the  entire 
amount  of  available  water  is  deliv- 
ered to  the  condenser,  and  a  supply 
from  the  catch  pan  (if  it  be  an  at- 
mospheric  type)  is  taken  for  the  water 
jackets,  in  which  case  a  greater  quan- 


Fig.  15. 


tity  may  be  used  but  at  a  higher  temperature.  It  is  customary 
to  admit  the  water  through  the  flange  forming  the  bottom  of  the 
water  jacket  and  overflow  near  the  top  into  a  stand  pipe  which  is 
connected  at  its  lower  end  through  the  flange  to  a  system  of  pipes 
to  take  it  away.  To  prevent  condensation  on  the  outer  surface  of 
the  jacket,  and  to  present  a  more  pleasing  appearance,  it  is  fre- 
quently lagged  with  hardwood  strips  and  bound  with  finished 
brass  or  nickel-plated  bands.  It  is  also  well  to  have  a  washout 
connection  from  each  jacket. 

Lubrication.  The  vertical  type  of  compressor  requires  the 
least  amount  of  lubrication  from  the  fact  that  all  moving  parts  are 
in  equilibrium.  The  slight  amount  of  oil  used  is  merely  to  keep 
the  surfaces  from  becoming  entirely  dry.  Excessive  lubrication 
is  an  objection,  owing  to  the  insulating  effect  upon  the  surfaces 


EEFKIGEKATICW 


31 


of  the  condensing  and  evaporating  system.  Therefore  it  is  well 
to  feed  to  the  compressors  as  little  as  is  consistent  with  the  opera- 
tion  of  the  machinery.  A  proper  separating  device  should  be 
located  in  the  discharge  pipe  from  the  compressor  to  the  con- 
denser. To  properly  admit,  or  feed  the  lubricant  to  the  com- 
pressors, sight  feed  lubricators  should  be  provided,  by  which  the 
amount  may  be  determined  and  regulated.  These  may  be  of  the 


Fig.  16, 

reservoir  type,  or  better  still  the  droppers,  fed  from  a  large  reser- 
voir through  a  pipe  and  which  may  be  filled  by  a  hand  pump 
when  necessary  (see  Fig.  16).  Owing  to  the  action  of  ammonia 
on  animal  or  vegetable  oils,  other  than  these  must  be  used  as  a 
lubricant  for  the  compressor.  The  principal  oil  for  this  purpose 
(and  when  obtained  pure,  a  very  good  one)  is  the  West  Virginia 
Natural  Lubricating  Oil  or  Mount  Farm,  which  is  a  dark-colored 
oil  not  affected  by  the  action  of  the  ammonia  or  the  low  tempera- 
ture of  the  evaporator.  Of  late  years  the  oil  refining  companies 
have  put  on  the  market  a  light-colored  oil  which  appears  to  give 
good  results  for  the  purpose.  Care  should  be  used,  however,  iw 


32  KEFKIGEKATION 


the  selection  and  oil  should  not  be  used  unless  it  is  of  the  proper 
grade,  as  serious  results  follow  the  use  of  inferior  oils.  The  usual 
result  is  the  gumming  of  the  compressors  and  valves  or  the 
saponifying  under  the  action  of  the  ammonia  through  the  system. 

LOSSES. 

Having  described  the  compressor  and  its  parts,  let  us  take  up 
the  losses  due  to  the  improper  working  or  assembling  of  the 
parts  of  the  machine,  before  proceeding  with  the  description  of 
the  rest  of  the  plant.  As  has  been  stated  in  a  general  way,  the 
economy  of  the  compressor  lies  in  its  filling  at  the  nearest  possible 
point  to  the  evaporating  pressure  and  then  compressing  and  dis- 
charging at  the  lowest  possible  pressure,  as  much  of  the  entire 
contents  of  the  cylinder  as  possible.  If  the  compressor  piston 
does  noc  travel  close  to  the  upper  end  (of  a  single-acting  ma- 
chine) or  the  machine  has  excessive  clearance,  the  compressed  gas 
remaining  in  the  cylinder  re-expands  on  the  downward  stroke  of 
the  piston  and  gas  from  the  evaporator  will  not  be  taken  into  the 
compressor  until  the  pressure  falls  to,  or  slightly  below,  this  point, 
and  the  loss  due  to  this  fault  is  equal  to  the  quantity  of  gas  thus 
prevented  from  entering  the  compressor  plus  the  friction  of  the 
machine  while  compressing  the  portion  of  the  gas  thus  expanding. 

If  we  make  a  full  discharge  of  the  gas  and  there  is  a  leaky 
outlet  valve  in  the  compressor,  the  escape  and  re- expansion  into 
the  compressor  affects  not  only  the  intake  of  the  gas  at  the  begin- 
ning of  the  return  stroke,  but  continues  to  affect  the  amount  of 
incoming  gas  during  the  entire  stroke  and  the  capacity  of  the  ma- 
chine  will  be  correspondingly  reduced.  If  the  inlet  valve  is  leaky 
or  a  particle  of  scale  or  dirt  becomes  lodged  on  its  seat,  as  the 
piston  moves  upward  the  portion  of  the  gas  which  may  escape 
during  the  period  of  compression  is  forced  back  to  the  evaporator 
and  a  corresponding  loss  is  the  result.  A  piston  which  does  not 
fit  the  compressor,' faulty  piston  rings,  or  a  compressor  which  has 
become  cut  or  worn  to  the  point  of  allowing  the  escape  of  gas 
between  the  cylinder  and  piston  has  the  same  effect  as  the  ill 
conditioned  suction  valve.  The  loss  due  to  leaky  or  defective 
cylinders,  joints  or  stuffing  boxes,  are  not  included  under  this 
head  as  these  more  generally  effect  the  loss  of  the  material  than 
the  efficiency  of  the  compressor. 


KEFKIGEKATIOST 


33 


To  present  graphically  the  losses  due  to  the  above  causes 
refer  to  Fig.  17,  which  illustrates  the  usual  indicator  card  taken 
from  an  ammonia  compressor  and  the  effect  upon  it  of  the  various 


The  different  mechanisms  employed  in  actuating  the  com- 
pressor piston,  such  as  crossheads,  connecting  rods,  pins,  crank 
shaft  and  bearings,  are  of  usual  engine  practice.  A  detailed 
description  will  not  be  given  here.  It  should  be  stated  that  owing 
to  the  steady  load  and  the  continuous  service  usually  demanded  of 


Fig.  17. 

a  refrigerating  plant,  and  the  occasional  high  pressures  encount- 
ered in  the  extremely  warm  W3ather,  the  construction  should  be 
of  the  best  and  the  wearing  surfaces  ample  to  withstand  the  hard 
service.  The  many  types  of  machines  and  the  methods  of  connect- 
ing the  power  or  engine  are  of  almost  endless  variety.  It  is  suf- 
ficient to  state  that  the  general  classes  of  engines  are  of  vertical  or 
horizontal  single-cylinder,  tandem  or  cross  compound,  condensing 
or  non  -condensing. 

The  horizontal  double-acting  compressor  embodies  all  the 
general  principles  of  the  vertical  single-acting,  but  having  certain 
modifications  to  meet  the  mechanical  differences  presented.  They 
may  be  divided  into  two  classes,  those  having  water  jackets  and 


84  KEFRIGEKATION 

those  without.  The  former  usually  has  a  water  jacket  extending 
about  the  body  of  the  cylinder  but  not  over  the  heads  and  valves 
as  in  the  single-acting  compressor.  Compressors  not  provided 
with  water  jackets  are  internally  cooled  either  by  evaporation  of  a 
portion  of  the  ammonia,  or  the  injection  of  ammonia  or  cooled  oil. 
The  claims  of  both  these  last  named  systems  are  that  instead  of 
the  curve  of  compression  being  close  to  .the  adiabatic  it  is  brought 
nearly  to  the  isothermal,  and  that  a  corresponding  economy  in 
horse  power  required  to  operate  the  machine  is  effected.  Owing 
to  the  fact  that  this  type  of  compressor  takes  in  and  discharges 
gas  in  both  directions,  it  is  necessary  that  inlet  and  outlet  valves 
be  provided  in  both  heads,  and  that  the  inner  head  be  provided 
with  a  stuffing  box  also  for  the  piston  rod.  This  renders  it  im- 
possible to  place  the  valves  horizontally,  and  as  a  result,  the  valves 
are  placed  at  an  angle  of  from  30°  to  45°  from  the  center  of  the 
compressor,  and  the  inner  face  of  the  heads  and  pistons  made  on 
an  angle  to  conform  to  this;  or  sometimes  the  valves  are  spherical, 
to  avoid  clearance  which  would  result  from  the  difference  in  their 
surfaces.  The  weight  of  the  piston  and  rod  being  towards  the 
bottom  of  the  cylinder,  it  is  necessary  that  the  piston  be  of  con- 
siderable length  to  provide  a  greater  surface  for  wear. 

The  stuffing  box  must  have  sufficient  depth  to  successfully 
retain  the  gas  .during  the  period  of  compression,  and  lubrication 
should  take  place  while  the  rod  is  passing  through  the  packing. 
This  is  accomplished  with  a  small  oil  pump  actuated  from  the 
moving  parts  of  the  machine  or  a  pressure  system  regulated  by 
the  pressure  in  the  oil  separator.  In  each  case  oil  passes  between 
the  double  packing  thereby  causing  the  piston  rod  to  pass  through 
a  chamber  of  oil. 

The  compressor  valves  and  their  cages  are  of  the  description 
already  given  and  the  same  care  and  caution  regarding  the  con- 
struction and  operation  apply  to  the  valves  of  this  type  of 
machine,  but  the  fact  that  they  are  horizontal  or  nearly  so  makes 
their  construction  somewhat  different  and  necessitates  springs  of 
different  strength.  The  valves,  cages  and  springs  are  covered  by  a 
dome  bolted  in  place  and  its  union  with  the  compressor  head  is 
provided  with  a  gasket  to  prevent  loss  of  ammonia,  it  is  well  to 
have  at  hand  duplicates  of  the  compressor  valves  and  springs,  as 


REFRIGERATION  35 


an  entire  valve  can  be  changed  in  less  time  than  it  takes  to  repair 
one  out  of  order.  As  the  machine  during  this  time  must  remain 
out  of  service,  it  is  customary  for  the  builders  to  supply  these  in 
duplicate.  After  a  valve  is  taken  out  and  replaced,  it  is  well  to 
have  the  faulty  one  put  in  perfect  condition,  the  strength  of 
springs  tested,  the  seat  and  stem  corrected,  oiled  and  put  away  in 
readiness  to  be  used  again  when  the  occasion  requires. 

This  type  of  compressor  is  usually  driven  from  a  rotating 
shaft  with  the  ordinary  connecting  rod  by  a  crank  and  crosshead. 
Adjustment  for  wear  is  provided  in  the  piston  rod  at  the  cross- 
head,  and  the  position  of  the  piston  may  be  adjusted  between  the 
heads  of  the  compressor  by  screwing  in  or  out  of  the  crosshead. 
The  clearance  of  the  compressor  piston  is  important;  it  should  be 
as  small  as  possible  and  yet  not  allow  the  piston  to  strike  the 
heads.  This  naturally  cannot  be  reduced  to  the  small  degree  pos- 
sible in  the  single-acting  type,  from  the  fact  that  it  must  be  ad- 
justed to  both  heads,  and  the  expansion  and  contraction  of  the 
piston  and  connecting  rod  and  wear  is  of  such  an  amount  as  to 
render  a  close  adjustment  impossible.  Fig.  18  is  a  sectional  cut 
of  a  modern  type  of  double-acting  compressor  with  water  jacket; 
Fig.  4  a  section  of  one  not  using  the'  water  jacket  and  Fig.  10  an 
elevation  of  either  in  combination  with  its  motive  power,  a  Corliss 
engine,  shaft,  fly  wheel,  etc. 

The  stuffing-box  oil  pump  is  shown  in  Fig.  16  which  illus- 
trates the  general  method  of  lubricating  the  compressor  piston,  the 
oil  being  pumped  through  the  box  and  returning  to  a  catch  pan 
or  basin  provided  in  the  bed  plate. 

THE  AMMONIA  CONDENSER. 

The  Ammonia  Condenser,  or  liquefier,  as  briefly  stated  in  the 
description  of  the  system,  is  that  portion  of  the  plant  in  which  the 
gas  from  the  evaporator,  having  been  compressed  to  a  certain 
point,  is  cooled  by  water  and  thereby  deprived  of  the  heat  which 
it  took  up  during  evaporation ;  consequently  it  is  reduced  to  its 
initial  state,  that  is,  liquid  anhydrous  ammonia.  Let  us  consider 
the  general  principles  governing  the  action  before  describing  the 
types.  On  account  of  the  duty  having  been  performed,  the 
ammonia  as  it  leaves  the  evaporator  is  a  gas  of  low  temperature, 


36 


REFEIGEEATION 


usually  5°  to  10°  below  that  of  the 
brine,  or  other  body  upon  which 
it  has  been  doing  duty,  yet  it  is 
laden  with  a  certain  amount  of 
heat,  although  at  a  temperature 
not  ordinarily  expressed  by  that 
term.  It  is  a  well-known  fact 
that  we  cannot  obtain  a  refriger- 
ating agent  which  can  absorb  heat 
from  a  body  colder  than  itself, 
and  it  is  therefore ,  necessary  to 
bring  the  temperature  of  the  am- 
monia gas  to  a  point  at  which  the 
flow  of  heat  from  the  one  to  the 
other  will  take  place.  This  is 
done  by  withdrawing  part  of  the 
heat  in  the  ammonia  in  the  fol- 
lowing manner:  The  cold  gas  is 
06  compressed  until  its  pressure 
ti  reaches  such  a  point  that  at  ordi- 
fe  nary  temperatures  it  will  condense 
to  liquid  form.  As  it  leaves  the 
compressor  it  is  very  hot  because 
t)f  the  fact  that  it  still  'Contains 
nearly  all  of  the  heat  it  had  when 
it  left  the  evaporator  in  only  a 
small  portion  of  the  space  occu- 
pied before.  Thus  when  it  reaches 
the  condenser  it  is  much  warmer 
than  the  cooling  water  and  will 
readily  give  up  its  heat  to  the 
cold  water — so  much  that  its  la- 
tent heat  is  absorbed  by  the  water 
and  it  condenses  into  anhydrous 
ammonia. 

The  temperature  of  water  if 
pumped  ironi  surface  streams  will 
average  about  60°  F  and  since  we 


KEFKIGEEATION 


37 


cannot  expect  to  get  the  ammonia  any  colder  than  this  it  must  be 
compressed  until  the  boiling  point  corresponding  to  the  pressure 
obtained  is  at  about  75°  F. 

In  the  table,  page  78,  we  find  that  this  temperature  corre- 
sponds to  a  pressure  of  144.25  pounds  per  square  inch  (absolute)  or 
126.55  pounds  per  square  inch  (gauge). 

Thus  if  the  gas  is  compressed  until  the  gauge  reads  126.55 
and  then  passed  into  a  condenser  where  the  temperature  of  tha 
water  is  less  than  75°  F  the  water  will  absorb  the  latent  heat  and 
we  have  accomplished  our  object  which  was  to  remove  some  of 
the  heat  contained  in  t  he  ammonia.  In  this  condition  it  is  drained 
from  the  condenser  into  the  ammonia  receiver  to  again  repeat  the 
cycle  of  operation. 

E 

/" 


Fig.  19. 

The  forms  of  condenser  may  be  divided  into  three  classes; 
the  submerged,  atmospheric,  and  double-pipe.  Of  each  of  these 
classes  a  number  of  different  types  and  constructions  are  in  use. 
To  illustrate  the  general  principles,  however,  it  is  only  necessary 
to  present  one  of  each  type. 

The  Submerged  Condenser  consists  of  around  or  rectangular 
tank  with  a  series  of  spiral  or  flat  coils  within  joined  to  headers  at 
top  and  bottom  with  proper  ammonia  unions.  In  Fig.  19  is 
shown  a  sectional  elevation  of  a  popular  type  of  submerged  con- 
denser.  A  wrought  iron  or  steel  tank  A  is  formed  by  plates  from 
-j^-  to  T5g-  inch  thick,  of  the  necessary  dimensions  to  contain  the 
coils,  and  sufficiently  braced  around  the  top  and  sides  to  prevent 
bulging  when  filled  with  water.  A  series  of  welded  zigzag  pipe 


88 


EEFKIGEEATION 


coils  B  are  placed  in  the  tank  and  joined  to  headers  0  with 
ammonia  unions  D.  The  ammonia  gas  enters  the  top  header 
through  the  pipe  E  and  an  outlet  for  the  liquefied  ammonia  is 
provided  at  F  with  a  proper  stop  valve.  Water  is  discharged  or 
admitted  to  the  tank  at  or  near  the  bottom  and  overflows  at  outlet 


M.  It  will  be  seen  that  in  this  type  of  condenser  a  complete 
reverse  flow  of  the  current  is  effected,  the  gas  entering  at  the  top 
and  the  liquid  leaving  at  the  bottom,  while  the  water  enters  at  the 
bottom  and  leaves  at  the  top,  thereby  bringing  the  coldest  water 
in  contact  with  the  coolest  gas .  and  the  warmer  water  in  contact 


REFKIGERATION  89 


with  the  incoming  or  discharged  gas  from  the  compressor,  thereby 
presenting  the  ideal  condition  for  properly  condensing  ammonia. 

Owing  to  the  necessarily  large  spaces  between  the  coils  and 
the  distance  between  the  bent  pipes,  the  portion  of  water  coming 
in  contact  with  the  surface  of  the  pipes  must  be  small  compared 
with  the  total  amount  passing  through;  it  is,  therefore,  uneconom- 
ical as  regards  amount  of  water  used.  With  water  containing  a  large 
amount  of  floating  impurities  the  deposit  on  the  coils  is  consider- 
able, and  not  easily  removed  owing  to  the  limited  space  between 
the  coils,  and  furthermore,  the  dimensions  of  the  tank  necessary 
to  contain  the  requisite  amount  of  pipe  for  a  plant  of  considerable 
size  is  so  great  and  its  weight  when  equipped  with  coils  and  filled 
with  water  requires  such  a  strong  support  that  its  use  is  now  lim- 
ited to  certain  requirements  and  localities. 

A  better  shape  for  a  condenser  of  this  type  is  one  of  consid- 
erable height  or  depth,  rather  than  low  and  broad.  This  is  owing 
to  the  fact  that  the  greater  the  length  of  travel  of  the  water  arid 
gas  in  opposite  directions,  the  greater  the  economy.  The  number 
of  coils  used  should  be  such  that  the  combined  internal  area  of 
the  pipes  equals,  or  exceeds  the  area  of  the  discharge  pipe  from  the 
compressor.  The  circular  submerged  condenser  is  similar  to  the 
above  described  except  that  the  tank  is  circular  and  the  coils  bent 
spirally. 

The  Atmospheric  type  of  condenser  most  generally  used  ia 
made  of  straight  lengths  of  2-inch  extra-strong,  or  special  pipe, 
usually  20  feet  long,  screwed,  or  screwed  and  soldered  into  steel 
return  bends  about  3J-inch  centers  and  usually  from  eighteen  to 
twenty-four  pipes  high.  The  coil  is  supported  on  cast  or  wrought 
iron  stands  and  placed  within  a  catch  pan,  or  on  a  Water-tight 
floor,  having  a  proper  waste  water  outlet  and  supplied  with  one  of 
the  several  means  of  supplying  the  cooling  water  over  their  sur. 
faces.  Stop  valves,  manifolds  and  unions  connect  with  the  dis- 
charge of  the  compressor  and  the  liquid  ammonia  supply  to  the 
receiver. 

In  the  manner  of  making  the  connections  to  this  type  of  con- 
denser  and  the  taking  away  of  the  liquefied  ammonia  as  well  as  in 
the  devices  for  supplying  the  cooling  water,  a  great  variety  exists; 
Fig.  20  represents  a  side  elevation  of  an  ammonia  condenser  with 


40 


EEFEIGEEATION 


the  discharge  or  inlet  of  the  gas  from  the  compressor  entering  at 
the  top  A  and  the  liquid  ammonia  taken  of?  at  the  bottom  B 
while  the  water  is  supplied  over  the  coils  flowing  down  into  the 


catch-pan  or  water-tight  floor  where  it  accumulates  and  is  taken 
away  by  any  of  the  usual  means.  It  will  be  noticed  that  the  flow 
of  the  water  and  gas  with  this  type  of  condenser  is  in  the  same 
direction,  the  coldest  water  coming  in  contact  with  the  warmest 


REFRIGERATION  41 


ammonia.  The  temperature  governing  or  determining  the  point 
of  condensation  will  be  that  of  leaving  the  condenser,  or  at  the 
bottom  pipe  in  which  the  liquid  ammonia  is  withdrawn.  Owing 
to  this  arrangement  it  is  not  favorable  to  a  low  condensing  pres- 
sure or  economy  in  the  water  used.  Fig.  21  represents  a  type  in 
which  an  attempt  is  made  to  eliminate  this  undesirable  feature, 
and  in  which  it  is  expected  to  use  the  waste  from  the  condenser 
proper,  in  taking  out  the  greater  part  of  the  sensible  heat  from  the 
gas  leaving  the  compressor. 

The  construction  of  this  condenser  is  identical  with  that  shown 
in  the  preceding  figure  except  that  its  uppermost  pipe  is  continued 
down  and  under  the  pipes  forming  the  condenser  proper;  it  passes 
backward  and  forward  in  order  that  a  large  proportion  of  the  heat 
may  be  removed  by  the  water  from  the  condenser  proper,  before 
the  ammonia  enters  the  condenser.  A  supplemental  header  is 
sometimes  introduced  in  connection  with  this  pipe  f<T  emoving 
any  condensation  taking  place  in  it. 

A  third  type  of  this  coitdenser  is  shown  in  Fig.  22.  In  this 
type  a  reverse  flow  of  the  gas  and  water  takes  place.  The  gas 
enters  the  condenser  through  a  manifold  or  header  A  at  the  bottom 
and  continues  its  flow  upward  through  the  pipes  to  the  top;  at 
several  points  drain  pipes  are  provided  for  taking  off  the  condensa- 
tion into  the  header  B.  The  condensing  water  flows  downward  over 
the  pipes.  The  form  is  the  most  nearly  perfect  condenser  of  the  class. 

The  atmospheric  type  is  a  favorite,  and  possesses  many  feat- 
ures that  make  it  preferred  to  the  submerged.  Its  weight  is  a 
minimum,  being  only  that  of  pipe  and  supports  and  a  small  amount 
of  water.  The  sections  or  banks  may  be  placed  a  favorable  distance 
apart  to  facilitate  cleaning  and  repairs,  while  the  atmospheric  effect 
in  evaporating  a  portion  of  the  condensing  water  during  its  flow 
over  the  condenser,  thereby  obtaining  the  advantage  of  its  latent 
heat  as  well  as  the  natural  raise  in  its  temperature,  adds  materially 
to  its  efficiency. 

The  various  devices  for  distributing  the  water  over  the  con- 
denser  are  numerous: 

Fig.  23  represents  the  simplest  and  most  easily  obtained;  a 
simple  trough  with  perforations  at  the  bottom  for  allowing  the 
water  t.g  drip  through  to  the  condenser. 


REFRIGERATION 


Fig.  24  is  a  modification  of  the  one  shown  in  Fig.  23.  This 
is  intended  to  prevent  the  clogging  of  the  perforations,  by  allow- 
ing  the  water  to  flow  into  the  space  at  one  side  of  the  partition, 
and  then  through  a  series  of  perforations  into  the  second,  and 


thence  through  a  second  set  of  perforations  in  the  bottom  to  the 
pipes  in  the  condenser. 

Fig.  25  is  a  type  of  trough,  or  water  distributor,  designed  to 
overcome  the  objections  to  a  perforated  form  of  trough,  and  the 
consequent  difficulties  due  to  the  clogging  or  filling  of  the  perfora- 


KEFKIGEKATION 


43 


tions.     As  will  be  readily  understood  from  the  illustration,  this  is 
also  made  of  galvanized  sheet  metal  with  one  side  enough  higher 


Fig.  23. 


Fig.  24. 

than  the  other  to  cause  the  water  to  overflow  through  the  V. 
shaped  notches  or  openings  along  the  top  of  the  straight  or 
vertical  side  of  the  trough,  and  down  and  off  the  serrated  bottom 
edge  to  the  pipes. 


REFRIGERATION 


The  object  of  the  serrated  edges,  as  will  be  apparent,  is  tlie 
more  even  distribution  of  the  water,  owing  to  the  fact  that  while 
it  would  be  practically  impossible  to  obtain  a  uniform  flow  of 
water  over  a  straight  and  even  edge  of  a  trough,  particularly  if 
the  amount  is  limited,  it  is  an  easy  matter  to  regulate  the  flow 
through  the  Y-shaped  openings. 

Fig.  26  is  termed  the  "slotted  water  pipe."  It  is  a  pipe 
slotted  between  its  two  ends,  from  which  the  water  overflows  to 
the  series  of  pipes  below.  It  is  good  practice  to  lead  the  water 
supply  to  a  cast-iron  box  at  the  center,  of  the  condenser,  into  the 


Fig.  25. 

sides  of  which  is  screwed  a  piece  of  pipe  (usually  2-inch)  reaching 
the  ends  of  the  condenser,  and  having  its  outer  ends  capped,  which 
may  be  removed  while  a  scraper  is  passed  through  the  slot  from 
the  center  towards  the  ends  while  the  water  is  still  flowing, 
thereby  carrying  off  any  deposit  within  the  pipe.  This  forms  a 
very  durable  construction,  and  not  liable,  as  with  the  galvanized 
drip  trough,  to  disarrangement  or  bending  out  of  shape  due  to 
various  causes.  It  is  impossible,  however,  to  obtain  the  uniform 
flow  of  water  over  the  condenser  with  this,  as  with  the  serrated  or 
perforated  troughs,  particularly  if  tfie  supply  is  limited,  from  the 
fact  as  stated  in  describing  the  overflow  trough,  viz:  the  impossi- 
bility of  obtaining  a  sufficiently  thin  stream  of  that  length. 


REFRIGEKATION 


The  Double=Pipe  Condenser  is  a  modern  adaptation  of  an  old 
idea,  given  up  owing  to  its  complex  construction  and  the  imper- 
feet  facilities  available  for  its  manufacture.  Also,  like  the  Brine 
Cooler,  it  has  come  into  use  with  great  rapidity,  and  has  brought 
forth  many  novel  ideas  of  principle  and  construction.  It  com- 
bines the  good  features  of  the  atmospheric  as  well  as  the  sub- 
merged; as  in  the  former  the  weight  is  small  and  it  is  accessible 
for  repairs.  It  has  the  downward  flow  of  the  ammonia  and  up- 
ward flow  of  the  water,  effecting  a  complete  counter  flow  of  the 
two.  minimizing  the  amount  of  water  required  and  taking  up  the 


O 


Fig.  26. 

heat  of  condensation  with  the  least  possible  difference  between  the 
ammonia  and  water. 

The  two  general  forms  of  construction  are  a  combination  of  a 
IJ-inch  pipe  within  a  2-inch  pipe,  or  a  2-irich  pipe  within  a 
3-inch.  The  water  passes  upward  through  the  inner  pipe,  while 
the  gas  is  discharged  downward  through  the  annular  space;  or, 
the  position  of  the  two  may  be  reversed,  the  ammonia  being 
within  the  inside  pipe  while  the  water  travels  upward  through  the 
annular  space.  They  are  also  constructed  in  series,  in  which  the 
gas  enters  a  number  of  pipes  of  a  section  at  one  time,  flowing 
through  these  to  the  opposite  end  to  a  header  or  manifold,  at 
which  point  the  number  of  pipes  is  reduced,  and  so  on  to  the 


BEFKIGERATION 


REFKIGEEATION 


4S 


REFEIGEEATIOK 


Vinr! — Inorf     "nnr! — FSrf    'nnr{__5^y 


REFRIGERATION 


bottom  with  a  constantly  reduced  area.  The  theory  of  this  con- 
struction being  that  the  volume  of  the  gas  is  constantly  reduced 
as  it  is  being  condensed. 

Figs.  27,  28  and  29  illustrate  a  general  range  of  the  various 
types  in  use. 

It  is  usual  in  the  construction  of  this  type  to  make  each 
section  or  bank  twelve  pipes  high 
by  about  17J  feet  long;  they  are 
rated  nominally  at  ten  tons  refrig- 
erating capacity  each,  although  for 
uneven  units  the  construction  is 
made  to  vary  from  10  to  14  pipes 
in  each. 

The  Oil  Separator  or  Interceptor 
is  a  device,  or  form  of  trap,  placed 
on  the  line  of  the  discharge  between 
the  compressor  and  the  condenser  to 
separate  ths  oil  from  the  ammonia 
gas.  It  is  to  prevent  the  pipe  sur- 
face of  the  condensing  and  evapor- 
ating system  from  becoming  covered 
with  oil  which  acts  as  an  insulator 
and  prevents  rapid  transmission  of 
heat  through  the  walls. 

The  construction  admits  of  quite 
a  variety  of  principle,  from  the  plain 
cylindrical  shell  with  an  inlet  at  one 
side  or  end  and  an  outlet  at  the 
other,  to  the  almost  endless  variety 
of  baffle  plates,  spiral  conductors 
and  reverse-current  devices.  The 
object  is  similar  to  that  of  the 


Fig.  30. 


or  exhaust  separator,  and  generally  speaking,  that  which  would 
be  effective  in  one  service  would  be  so  in  the  other.  Figs.  30,  31 
and  3 2  illustrate  three  of  the  most  common  types  in  use;  from  these 
the  student  will  understand  the  general  principles. 

AMMONIA  RECEIVER. 

The  Ammonia  Receiver  or  Storage  Tank  is  a  cylindrical  shell 


50 


KEFBIGEKATIOlSr 


with  heads  bolted  or  screwed  on,  or  welded  in  each  end,  and  pro. 
vided  with  the  necessary  openings  for  the  inlet  and  outlet  of  the 
ammonia,  purge-valve  and  gauge  fittings.  They  may  be  vertical 
or  horizontal ;  the  former  type  is  generally  used  on  account  of  the 
saving  of  floor  space,  while  the  horizontal  is  necessary  when  the 
condenser  is  located  so  low  as  to  make  the  flow  of  the  liquid 
ammonia  into  the  vertical  type  impossible.  A  convenient  location 
for  the  receiver  in  a  plant  in  which  the  condenser  is  located  above 

the  machine  room,  is 
against  the  wall,  or  at 
one  side  of  the  room 
on  a  bracket  or  stand 
at  one  side  of  the  oil 
interceptor,  the  sizes 
of  the  twro  beinof  efen- 

o  o 

arally  the  same.  They 
are  then  more  readily 
under  the  control  of 
the  engineer  than  if  at 
some  out  of  the  way 
place. 

Fig.  33  illustrates  a 
receiver  of  the  verti- 
cal type  with  the  usual 
valves  and  connec- 
tions for  the  proper 
equipment.  The  liq- 
uid ammonia  enters  at 
the  top  and  is  fed  to 
the  evaporator  from 
the  side  near  the  bot- 
tom, the  space  below 
this  opening  being 
provided  for  tha  accumulation  of  scale,  dirt,  or  oil,  and  means  are 
provided  for  drawing  off  through  the  purge  valve  in  the  bottom. 

PIPES,  VALVES  AND  FITTINGS. 

Pipes.     Extra  strong,  or  extra  heavy  pipe  (so  called)  is  the 
generally  accepted  pipe  for  connecting  the  various  parts  of  the 


Fig.  31. 


Fig.  32. 


EEFKIGEKATIOff 


51 


refrigerating  system.  "Wrought- iron  pipe  is  generally  preferred 
to  steel.  Frequently,  however,  and  particularly  for  the  evapor- 
ating or  low-pressure  side  of  the  system,  a  special  weight  or  grade 
of  pipe  is  used,  also  standard  or  common  pipe  is  sometimes  em- 
ployed for  this  purpose.  Without  knowing  the  particular  condi- 
tions under  which  this  is  to  be  used,  or  the  relative  value  of  the 
material,  or  manner  in  which  the  pipe  is  made,  it  is  always  better 
to  use  and  insist  on  having  the  standard  extra-strong  grade.  The 
threads  should  be  carefully  \jut,  with  a 
good  sharp  die,  making  sure  that  the  top 
and  bottom  of  the  threads  are  sharp  and 
true.  With  this  precaution,  and  an 
equally  good  thread  in  the  fitting,  it  is 
not  difficult  to  form  a  good  and  lasting 
joint.  Particular  care  should  also  be 
taken  that  the  pipe  screws  into  the 
fitting  the  proper  distance,  and  forms  a 
contact  the  entire  length,  rather  than  to 

O          ' 

screw  up  against  a  shoulder  without  8 
perfect  fit  in  the  thread.  This  latto? 
often  causes  leaky  joints  sometime  after 
the  plant  has  been  operated  •  the"  tempo- 
rary joint  formed  by  screwing  in  too 
deep  against  the  shoulder  or  ill-fitting 
threads  very  often  passes  the  test  and  is 
used  for  some  time  after  until  the  com- 
bined effect  of  heat  and  cold,  and  action 
of  the  ammonia  cause  it  to  break  out. 
It  is  a  safe  rule  that  no  amount  of  solder 
or  other  doctoring  that  is  not  backed  up 

by  a  good  fitting  thread  to  support  it  can  make  an  ammonia  joint. 
This  is  particularly  true  of  the  discharge  or  compression  side  of 
the  plant. 

The  manner  of  making  these  joints,  may  be  divided  into  those 
having  a  compressible  gasket  between  the  thread  on  the  pipe  and 
the  fitting  into  which  it  screws  and  the  screwed  joint  formed  by  a 
threaded  pipe  screwed  into  a  tapped  flange  or  fitting.  The  latter 
may  be  divided  into  those  having  a  soldered  joint,  or  one  in  which 


REFRIGERATION 


the  union  is  formed  by  the  threads  only,  with  some  of  the  usual 
cements  to  assist  in  making  a  tight  joint. 

The  two  most  prominent  types  of  gasket  fittings  are  shown  iu 
Fig.  34  and  35.  The  former  is  known  in  this  'country  as  the 
Boyle  Union,  and  is  extensively  used.  As  will  be  observed,  the 
drawing  together  of  the  two  glands  by  the  bolts,  compresses  the 

gaskets,  (usually  rubber) 
against  the  threaded  sides 
of  the  pipe,  the  bottom 
and  sides  of  the  recess  in 
the  flanges,  and  the  edges 
of  the  ferrule  between  the 
two  gaskets. 

Fig.  35  represents  a 
union  or  joint  quite  fre- 
quently used,  although  not 
as  commonly  as  the  former,  , 
In  this  the  pipe  is  threaded 
and  screwed  into  the  body 
of  the  fitting,  but  not  to 
form  an  ammonia-tight 
joint;  leakage  is  prevented 
by  a  packing  ring  com- 
pressed  by  the  gland  against 
the  pipe  thread  and  the 
walls  of  the  recess. 

In  Fig.  36  (a  type  ol 
ammonia  coupling),  the 
contact  between  the  pipe 
and  fitting  is  made  to  with. 
stand  the  leakage  of  the 
gas  without  the  aid  of  pack- 
ing or  other  material  other  than  solder  or  some  of  the  usual 
cements;  the  two  flanges  are  bolted  together  with  a  tongue  and 
grooved  joint  having  a  soft  metal  gasket.  This  makes  a  permanent 
and  durable  fitting. 

Other  fittings  of  the  class,  as  ells,  tees,  and  return  bends,  are 
usually  provided  with  one  of  the  above  methods  of  connecting  with 


34t 


"I 

W      HH 


REFRIGERATION 


53 


the  system,  and  the  different  types  described  may  be  obtained  of 
the  builders  of  refrigerating  machines. 

Valves  for  the  ammonia  system  of  a  refrigerating  plant  are  of 
special  make  and  construction,  being  of  steel  or  semi -steel,  with  a 
soft  metal  seat  which  maybe  renewed  when  worn,  and  metal  gaskets 
between  the  bonnets  and  flanges. 

The  usual  types  are  Globe,  Angle  and  Gate,  subdivided  into 
screwed  and  flanged.  Fig.  37  is  a  generally  adopted  type  of  the 
flanged  globe  ammonia  valve,  while  Fig.  38  represents  the  angle 
valve  of  the  same  construction.  This  seems  to  represent  the  best 
elements  of  a  durable  and  efficient  valve. 


Fig.  35. 

For  a  valve  or  cock  requiring  a  fine  adjustment  as  is  frequently 
the  case  in  direct -expansion  systems,  particularly  where  the  length 
of  the  evaporating  coil  or  system  is  short,  a  Y-shaped  opening  is 
desirable.  Fig.  39  represents  a  cock  for  this  purpose  which  will 
be  found  to  be  effective  and  meet  the  most  exacting  requirements. 

Pressure  Gauges.  Two  gauges  are  necessary  for  an  ammonia 
plant  of  a  single  system;  one  to  indicate  the  discharge  or  con- 
densing pressure,  and  one  for  the  evaporator  or  return  gas  pressure 
to  the  compressors. 

Owing  to  the  action  of  ammonia  on  brass  and  copper  the 
gauges  for  this  purpose  differ  from  the  ordinary  pressure  gauge  in 
that  it  is  made  with  a  tube  and  connections  of  steel  instead  of  brass, 
and  this  construction  is  the  general  choice  of  gauge  makers;  in 
other  respects  the  construction  is  similar.  For  machines  of  small 


REFRIGEKATION 


capacity  instruments  with  6 -inch  dials  are  common,  while  for  larger 
plants  8 -inch  is  the  generally  adopted  size.  The  graduation  for 
the  high  pressure  gauge  is  usually  to  300  pounds  pressure,  and  if 
a  compound  gauge  is  used,  it  is  made  to  read  to  a  vacuum  also. 
This  latter  is  only  needed  on  certain  occasions  and  frequently 
omitted  from  the  high-pressure  gauge.  Owing  to  the  necessity  of 
removing  the  contents  of  the  system  at  certain  times  and  usually 
through  the  evaporating  side  of  the  plant,  the  gauge  for  this 

portion  of  the  system  is  graduated 
to  read  from  a  vacuum  to  120  pounds 
pressure. 

In  connecting  the  gauges  to  the  sys- 
tem, it  is  customary  to  locate  the 
opening  in  the  discharge  and  return 
gas  lines  near  the  machine  within  the 
engine  room,  placing  a  stop  valve  at 
some  convenient  point  and  carrying 
a  line  of  ^  or  -J  inch  extra  strong 
pipe  to  the  gauges,  making  the  joints 
with  the  usual  ammonia  unions.  On 
account  of  the  possibility  of  leakage 
of  ammonia  gas  from  the  gauge  tube, 
it  is  often  considered  advisable  to  fill 
the  gauge  pipe  with  oil  (of  the  kind 
used  for  lubricating  the  ammonia 
compressor)  for  a  short  distance  above 
the  gauges,  upon  which  the  pressure 
of  the  gas  will  act,  causing  the  gauge 
to  move  properly  but  without  allowing  the  ammonia  gas  to  enter 
the  gauge.  This  is  an  application  of  the  same  principle  as  the 
steam  syphon  or  bent-pipe  arrangement  in  use  with  steam  gauges, 
for  the  purpose  of  keeping  the  heat  and  action  of  steam  from  the 
gauge  mechanism  by  the  retaining  of  water  in  the  gauge  con- 
nection. 

Other  gauges  used  about  the  refrigerating  plant  are  of  the 
ordinary  pressure  or  vacuum  types  and  do  not  need  a  special  de- 
scription, as  their  construction  and  manner  of  applying  to  the 
different  parts  of  the  system  are  well  known  to  the  engineer.  It 


KEFKIGEEATION 


Fig.  37. 


KEFKIGEEATION 


may  be  well,  however,  to  caution  the  user  on  the  importance  of 
testing  the  gauges  often  enough  to  be  sure  they  are  accurate,  as 
serious  damages  may  result  from  a  wrong  indication  of  pressure. 

BRINE. 

Brine  is  used  in  refrigeration  as  a  medium  for  the  transmis- 
sion of  heat  from  the  point  or  object 
to  be  refrigerated,  to  the  ammonia  or 
other  refrigerant,  and  accordingly  may 
be  found  in  plants  in  which  the  appli. 
cation  is  indirect. 

In  the  refrigerating  practice  of  today, 
two  kinds  of  brine  are  in  use,  chloride 
of  calcium,  and  chloride  of  sodium 
(common  salt).  Either  one  is  dissolved 
in  water  making  a  solution  of  the 
proper  density;  it  is  then  pumped  from 
the  brine  tank  or  cooler  to  the  objects  to 
be  refrigerated,  and  returned  by  a  sys- 
tem of  pipes  to  be  recooled  and  again 
circulated  through  the  refrigerating 
system. 

Chloride  of  calcium  brine  may  be 
made  of  such  density  that  its  freezing 
point  is — 54°  Fahr.  (54°  below  zero) 
while  chloride  of  sodium  (salt)  brine  of 
maximum  density  or  strength  freezes 
at  0°  Fahr.  It  will,  therefore,  be  seen 
that  for  very  low  temperatures  calcium 
brine  should  be  used.  For  brine 
coolers  in  which  the  briiie  passes 
through  the  pipes,  and  the  ammonia  is 
evaporated  on  the  outside  with  a  tern- 
perature  of  a  few  degrees  below  zero,  and  the  brine  not  in  active 
circulation,  salt  brine  would  be  frozen,  bursting  the  pipes  and 

causing  a  considerable  loss.  The  calcium  brine  may  be  made  of 
such  density  or  strength  as  to  make  this  impossible.  It  will, 
therefore,  be  evident  that  for  use  in  connection  with  a  brine 


Fig.  39. 


BEFRIGEEATION  57 


cooler,  the  chloride  of  calcium  brine  is  necessarily  the  choice 
It  also  has  no  corroding  effect  on  pipes,  pumps  or  other  connec- 
tions, and  while  the  cost  is  somewhat  more  than  that  of  salt,  the 
general  advantages  are  decidedly  in  its  favor. 

For  the  brine  tank  and  coil  system  of  refrigeration  salt  brine 
may  be  safely  used,  and  is  largely  used  at  the  present  time.  The 
evaporation  of  the  ammonia,  being  within  the  pipes,  can  only 
effect  the  freezing  of  a  small  portion  on  the  outer  surface,  and 
without  damage  to  the  plant.  As  its  temperature  may  be  reduced 
to  zero,  or  even  below  (if  circulation  be  maintained)  it  is  effective 
for  practical  purposes  wherein  the  temperature  required  is  not 
below  that  point.  The  proper  density,  or  strength  of  brine,  either 
calcium  or  salt  is  determined  by  the  temperature  to  which  it  is 
necessary  to  be  reduced,  and  the  tables  on  pages  79  and  80  will  be 
found  valuable  in  determining  the  proper  strength  for  different 
requirements.  It  should  be  remembered,  however,  that  a  differ- 
ence of  from  5°  to  10°  Fahr.  exists  between  the  temperature  of 
the  brine  and  that  of  the  evaporating  ammonia,  and  that  while  the 
strength  of  the  brine  may  appear  ample  for  the  temperature  at 
which  it  is  carried,  the  lower  temperature  of  the  evaporating 
ammonia  may  cause  it  to  solidify  within  or  upon  the  surface  of 
the  evaporator,  thus  causing  it  to  separate,  or  freeze,  and  act  as  an 
insulator  and  prevent  the  transmission  of  heat  through  the  surface. 
It  is,  therefore,  necessary  in  examining  into  the  strength  of  the 
brine,  to  consider  it  with  reference  to  the  evaporating  pressure  of 
the  ammonia  as  well  as  its  own  temperature. 

In  the  last  column  of  the  tables  is  given  the  gauge  pressure, 
corresponding  to  the  freezing  point  of  the  brine  of  different 
strengths. 

The  usual  and  proper  instrument  for  determining  the  strength 
of  brine  is  the  Beaume  scale,  for  chloride  of  calcium  brine.  A 
weighted  glass  tube  and  bulb  (Fig.  40)  is  graduated  0  to  100,  the 
former  being  its  floating  point  in  wrater  and  the  latter  the  floating 
point  in  a  saturated  solution  of  salt  brine.  By  comparison  of  the 
two  in  the  table  of  calcium  brine  it  will  be  observed  that  the  ratio 
of  the  two  scales  are  as  1  to  4  which  makes  it  possible  to  obtain 
one  from  the  other. 

In  using  the  scales  it  is  customary  to  draw  a  sample  of  the 


REFRIGERATION 


brine  in  a  glass  test  tube,  raising  its  temperature  to  approximately 
60°  Fahr.  and  insert  the  scale;  it  will  then  float  at  the  point  on  its 
scale  corresponding  with  its  strength. 

Brine  Systems.     In  the  use  of  the  foregoing  tables  for  cal- 
cium or  salt  brine,  allowance  should  be  made  for  the  difference  in 
the  grades  obtained.     The  quantity  required  per  gallon,  or  cubic 
foot  of  brine,  will  vary  accordingly.    The  average  quantity  required 
however,  should  nearly  correspond  with  the  tables. 

In  making  brine  it  is  well  to  lit  up  a  box  with  a  perforated 
false  bottom,  or,  a  more  readily   obtained  and  equally   effective 
mixer  may  be  made  by  taking  a  tight  barrel  or  hogshead,  into 
which  is  fitted  a  false  bottom  four  to  six  inches  above  the  bottom 
head,  and  which  is  bored  with  one-half  inch 
holes.     Over  the  false  bottom  lay  a  piece  of 
coarse  canvas  or  sack  to  prevent  the  salt  fall- 
ing through.     A  water  connection  is  made  in 
fjjj^jlijp  the  side  of  the  barrel  near  the  bottom,  between 

the  bottom  head  and  the  false  bottom,  and  a 
controlling  valve  placed  nearby  to  regulate 
the  amount  of  water  passing  through.  An 
overflow  connection  is  made  near  the  top  of 
the  cask,  with  its  end  so  placed  that  the  brine 
will  flow  into  the  tank,  and  a  wire  screen 
placed  across  its  end  inside  the  cask  with  a 
liberal  space  between  it,  and  the  opening,  to 
allow  of  cleaning.  See  Fig.  41.  The  cask  or 
barrel  is  now  filled  with  the  calcium  or  salt, 
which  dissolves  and  overflows  into  the  brine 
tank. 

A  test  tube  and  Beaume  scale,  or  salom- 
eter,  should  be  kept  at  hand,  and  frequent 
tests  made;  the  strength  may  be  regulated 
by  admitting  the  water  more  or  less  rapidly.  After  the  first 
charge  it  is  well  to  allow  the  mixer  to  remain  in  position  for 
future  requirements.  A  connection  should  be  made  from  the 
return  brine  line  from  the  refrigerating  system  to  the  cask,  with  a 
controlling  valve  by  the  use  of  which  the  strength  or  density  of  the 
brine  may  be  increased  without  adding  to  the  quantity,  keeping 


Fig.  40 


KEFKIGEKATION 


59 


the  cask  full  of  the  calcium  or  salt,  and  allowing  a  portion  of  the 
return  flow  of  brine  to  pass  through  the  cask,  dissolving  the  con- 
tents and  flowing  into  the  tank. 

Calcium  is  usually  obtained  in  sheet-iron  drums,  holding 
about  600  pounds  each;  it  is  in  the  shape  of  a  solid  cake  within 
the  drum.  It  is  advisable  to  roll  these  onto  the  floor  or  top  of 
tank  in  which  the  brine  is  to  be  made  and  pounded  with  a  sledge 
hammer  before  removing  the  iron  casing,  this  process  breaking  it 
up  into  small  pieces  without  its  flying  about  the  room.  After 
breaking  it  up  the  shell  may  be  taken  off  and  the  contents  shov- 

into  the  mixer. 


Fig.  41. 

It  is  also  sold  and  shipped  in  liquid  form,  in  tank  cars, 
generally  in  a  concentrated  form  (on  account  of  freight  charges) 
and  diluted  to  the  proper  point  upon  being  put  into  the  plant. 
Where  proper  railroad  facilities  exist,  this  is  probably  the  most 
desirable  way  of  obtaining  the  calcium. 

Salt  is  sold  and  may  be  obtained  in  .a  number  of  forms.  The 
usual  shape  for  brine  is  the  bulk,  or  in  sacks  of  about  200  pounds 
each.  "Where  it  is  possible  to  handle  salt  in  bulk,  direct  from  the 
car  to  the  tank,  this  is  most  generally  used  on  account  of  the 
price,  being  about  $1.00, per  ton  less  than  if  sacked.  If  it  is 
necessary  for  it  to  be  carted  or  stored  before  using,  the  sacjs  form 
is  preferable.  The  coarser  grades  of  salt  are  used  for  this  pur- 
pose,  No.  2  Mine  being  the  grade  commonly  used.  The  finer 


60  REFRIGERATION 


salts  are  higher  in  price,  without  a  corresponding  increase  iu 
strength  of  the  brine  formed. 

The  proper  density  or  strength  of  the  brine  must  be  deter- 
mined for  various  temperatures.  As  a  rule  its  freezing  point  should 
be  equal  to,  or  slightly  below,  the  temperature  of  the  evaporating 
ammonia,  rather  than  the  temperature  of  the  coldest  brine,  as  is 
common.  Referring  to  the  table  of  salt  brine  solution,  page  80; 
if  we  wish  to  carry  a  temperature  of  10°  Fahr.  in  the  outgoing 
brine,  it  is  necessary  that  the  temperature  of  the  evaporating  am- 
monia be  from  5°  to  10°  degrees  below  that  point,  in  order  that 
the  transfer  of  heat  from  the  brine  to  the  ammonia  will  be  rapid 
enough  to  be  effective,  which  would  mean  that  the  ammonia  would 
be  evaporating  at  a  temperature  of  practically  0°  Fahr.  To  pre- 
vent the  brine  freezing  against  the  walls  'of  the  evaporator  its 
strength  or  density  should  be  made  to  correspond  with  this,  or 
from  95°  to  100°  on  the  salometer.  This  should  be  cared  for 
more  especially  in  connection  with  plants  using  the  brine  cooler,  in 
which  the  brine  is  within  the  coil,  than  in  the  brine  tank  system 
in  which  the  ammonia  is  inside  the  pipe  and  the  brine  outside; 
here  the  only  danger  or  loss  would  be  in  efficiency. 

In  examining  into  the  causes  of  failure  in  a  plant  to  perform 
its  usual  or  rated  capacity,  it  is  advisable,  unless  there  is  every 
evidence  that  the  trouble  is  elsewhere,  to  make  an  examination  of 
the  brine  and  determine  that  its  strength  and  condition  is  suited 
to  the  duty  to  be  performed. 

DIRECT  EXPANSION. 

As  its  name  would  imply,  this  system  of  refrigeration  is  one 
in  which  the  refrigerant  is  expanded  or  evaporated  in  direct  contact 
with  the  duty  to  be  performed,  without  an  intermediate  agent  for 
the  transfer  of  the  heat.  Its  application  admits  of  quite  a  variety 
of  apparatus  to  meet  the  requirements  of  refrigerating  practice,  the 
most  general  of  which  is  the  expansion  within  a  pipe  system  placed 
in  a  room  to  be  refrigerated,  or  within  or  between  a  series  of  pipes 
over  or  within  which  the  substance  to  be  refrigerated  is  passed. 

While  the  former  system  admits  of  a  variety  of  arrangements 
of  the  pipes  within  the  room  or  chamber  to  be  refrigerated,  it  is 
confined  to  the  simple  principle,  however,  of  the  evaporation  of  the 
refrigerant  within  the  pipes,  by  the  transfer  of  heat  through  the 


REFRIGERATION 


61 


walls  of  the  pipe,  thereby  reducing  the  temperature  in  the  room  or 
chamber  to  the  desired  point,  and  for  certain  purposes  is  a  very 
satisfactory  means  of  producing  the  desired  results.  This  is  prin- 
cipally true  with  large  rooms  in  which  the  temperature  and  duty 
to  be  performed  is  constant,  such  as  a  brewery,  packing  house,  and 
cold-storage  rooms.  For  rooms  requiring  an  unusually  low  tem- 
perature, as  freezers  of  fish  and  poultry,  direct  expansion  is  desir- 
able, because  it  is  possible  to  more  nearly  reach  the  temperature  of 


Fig.  42. 


the  refrigerant  direct,  than  with  an  intermediate  agent,  as  brine; 
this  is  due  to  the  fact  that  there  must  necessarily  be  a  difference  of 
from  5°  to  10°  between  the  temperatures. 

Fig.  42  illustrates  a  direct  expansion  construction  in  which  the 
liquid  anhydrous  ammonia  is  expanded  by  the  valve  or  cock  A  into 
the  coil  or  system  of  pipes  B  and  the  gas  returning  to  the  com- 
pressor  through  the  pipe  C. 

Fig.  43  represents  a  fish-freezing  room  on  either  side  of  which 
is  arranged  a  series  of  pipe  shelves,  through  which  the  ammonia  is 
evaporated.  The  fish  are  laid  on  tin  trays  and  placed  on  the  pipe 


KEFK1GEKAT1OK 


shelves  until  the  room  is  filled.  It  is  then  closed,  the  ammonia 
turned  on  and  left  until  the  freezing  has  been  accomplished. 

It  is  apparent  from  the  arrangement  of  the  coils  being  both 
above  and  below  the  trays  holding  the  fish,  and  close  together,  that 
the  effect  must  be  very  rapid.  9 

In  the  cooling  of  J?eer^or  other  liquids,  two  forms  of  apparatus 
are  used :  one  (the  most  common),  being  a  series  of  a  2-inch  pipe  with 
return  bends,  stands,  etc.,  over  which  the  liquid  to  be  cooled  is  flowed 


Fig.  43. 

and  within  which  the  ammonia  is  evaporated,  the  product  being 
accumulated  in  an  iron  pan  or  other  receptacle  in  which  the  cool- 
ing pipes  are  placed.  In  brewery  practice  it  is  customary  to  pro- 
vide  a  double  series  of  coils,  one  above  the  other,  cold  water  being 
circulated  through  the  upper  section,  and  the  ammonia  through 
the  lower,  the  effect  of  which  is  first  to  remove  the  heat  from  the 
wort  as  far  as  possible  by  the  use  of  water,  and  the  remainder  of 
the  cooling  being  accomplished  by  the  evaporation  of  the  ammonia. 
This  apparatus  is  called  the  Baudelot  Cooler  and  is  illustrated  in 
Fig.  44. 

Fig.  45  represents  a  section  of  a  double -pipe  cooler  for  water 
or  other  liquids  and  is  similar  to  the  form  of  double-pipe  con- 
denser or  cooler  already  described.  It  varies  only  in  the  construc- 
tion of  the  inner  tube  which  is  corrugated  to  prevent  bursting  by 
freezing,  which  becomes  possible  when  used  to  cool  a  congealable 


.REFRIGERATION  63 


liquid.  In  the  operation  of  this  type  of  cooler,  when  used  as  an 
evaporator  or  direct  -expansion  cooler,  it  is  usual  to  reverse  the 
two  currents,  by  feeding  or  expanding  the  ammonia  into  the  bot- 
tom of  the  coil  the  gas  issuing  from  the  top,  while  the  liquid  to 
be  acted  upon  enters  at  the  top  of  the  coil  and  issues  from  the 
bottom.  This  type  of  cooler  is  largely  used  in  cooling  carbonated 
ale,  as  it  must  be  kept  from  the  atmosphere,  and  for  cooling  drink- 
ing water  in  circulating  systems  now  installed  in  hotels,  office 
buildings  and  department  stores. 

Purging  and  Pumping  out  Connection.  A  common  cause  of 
failure  to  operate  properly  and  effectively  is  the  introduction  of 
some  foreign  substance  into  the  system.  This  will  be  readily 
understood  and  appreciated  by  engineers  and  those  familiar  with 
the  requirements  of  a  steam  boiler.  Clean  surfaces  on  the  shell 
or  tubes  are  necessary  for  the  maximum  evaporation  of  water,  or 
the  transfer  of  heat  through  the  walls  of  pipe  or  other  forms  of 
heat-transmitting  surface.  The  most  common  difficulty  encoun- 
tered in  a  refrigerating  plant  is  oil,  either  in  its  natural  condition, 
or  saponified  by  contact  with  the  ammonia,  water  or  brine.  It 
enters  the  system  in  many  ways:  through  leakage,  condensation  in 
blowing  out  the  coils  or  system,  foreign  gas  arising  from  decom- 
position  of  the  ammonia  through  excessive  heat  and  pressure,  or 
the  mingling  of  air  which  may  enter  the  system  through  pumping 
out  below  atmospheric  pressure  or  the  air  may  have  remained  in 
the  system  from  the  time  of  charging,  never  having  been  fully 
removed.  It  is  also  probable,  though  hard  to  determine  with  cer- 
tainty owing  to  the  various  conditions  surrounding  the  operation  of 
plants,  that  impurities  are  introduced  with  the  ammonia,  either  as  a 
liquid,  gas  or  air  which  afterwards  becomes  impossible  to'condense. 

The  oil  in  a  system  forms  a  covering  or  coating  on  the  evap- 
orating surface  which  acts  as  an  insulation  and  prevents  the  ready 
transfer  of  heat  through  the  walls  of  the  evaporator.  The  pres- 
ence of  water  or  brine  causes  an  absorption  of  a  portion  of  the 
ammonia  into  the  water  or  brine,  forming  aqua  ammonia  which 
raises  the  boiling  point  of  the  ammonia  and  causes  material  loss  in 
the  duty.  Air  or  other  non -condensable  gas  in  the  system,  excludes 
an  equal  volume  of  the  ammonia  gas,  thereby  reducing  the  avail- 
able condensing  surface  in  that  proportion. 


64 


KEFEIGEEATIOK 


For  the  purpose  of  cleaning  the  system  and  removing  the 
different  impurities  which  may  appear,  purge  and  blow-off  valve? 
and  connections  are  provided.  One  of  these  is  placed  at  or  nea) 
the  bottom  of  the  oil  interceptor,  which  is  located  between  the 


compressors  and  the  condenser;  it  is  used  to  draw  of?  the  oil  used 
as  a  lubricant  in  the  compressor  and  precipitated  to  the  bottom. 
This  oil  should  not  be  allowed  to  accumulate  to  any  great  extent 
as  it  may  be  carried  forward  to  the  condenser  by  the  current  of 
the  gas. 


REFKIGERATIOK  65 


If  the  liquid  ammonia  receiver  be  placed  in  a  vertical  position 
it  is  customary  to  place  a  purge  valve  in  the  bottom  for  drawing 
off  oil  or  other  impurities.  The  supply  of  liquid  to  the  evaporator 
being  taken  off  at  a  short  distance  above  the  bottom  say  4  to  6 
inches. 

The  next  point  for  the  removal  of  impurities  is  at  the  bottom 
of  the  brine  cooler,  or  lowe"  manifold  of  the  coil  system  in  a  brine- 
tank  refrigerator.  These  may  be  tried  as  often  as  necessary  to 
determine  the  state  of  cleanliness  of  the  system.  If  the  system  is 
charged  with  any  of  the  common  impurities,  they  should  be  blown 
out  and  the  system  cleansed  at  the  earliest  possible  moment,  as 
they  cause  a  decided  loss. 

Air  or  foreign  gases  accumulate  in  the  condenser  because  the 
constant  pumping  out  of  the  evaporating  system  tends  to  remove 
them  from  that  part  of  the  system  to  the  condenser.  This  point, 
therefore,  is  the  most  natural  place  for  their  removal.  For  this 
purpose  it  is  customary  on  the  best  condensers  to  place  a  header  or 
manifold  at  the  top  at  one  end,  and  connect  each  of  the  sections  or 
banks  with  a  valved  opening.  A  valve  is  also  placed  at  each 
end  of  the  header,  and  a  connection  from  one  end  of  this  header 
made  to  the  return  gas  line  between  the  evaporator  and  the  com- 
pressors.  By  closing  the  stop  valves  on  the  gas  inlet  and  liquid 
outlet  of  any  one  of  the  sections  and  opening  the  purge  or  pump- 
ing-out  line  into  the  gas  line  to  the  compressors,  the  section  or 
bank  may  be  emptied  of  its  contents  for  repairs  or  examination 
arid  then  connected  up  and  put  into  service  without  shutting  down 
the  plant,  or  a  material  loss  of  ammonia.  For  purging  of  air  or  gas, 
the  valve  should  be  closed  between  this  header  and  the  machine, 
and  the  valve  on  the  opposite  end  opened  to  the  atmosphere,  the 
valves  on  each  section  opened  slightly  in  turn  while  the  foreign 
gases  are  expelled.  This  process  should  not  be  used  while  the 
compressor  is  in  operation,  as  the  discharge  of  the  ammonia  into 
the  condenser  would  keep  the  gas  churned  to  the  extent  that  it 
would  become  impossible  to  remove  the  foul  gases,  without  remov- 
ing a  considerable  portion  of  the  ammonia  also. 

For  this  reason  it  is  customary  before  blowing  off  the  con. 
denser  to  stop  the  compressor  and  allow  the  water  to  flow  over  the 
condenser  until  it  is  thoroughly  cooled.  Sufficient  time  should 


EEFEIGEBATION 


REFRIGERATION  67 


elapse  for  the  ammonia  to  liquefy  and  settle  towards  the  bottom, 
while  the  air  and  lighter  gases  rise  to  the  top,  at  which  point  they 
may  be  blown  out  through  the  purge  valve  to  the  atmosphere.  If 
doubt  exists  as  to  whether  ammonia  or  impurities  are  being  blown 
out  attach  a  piece  of  hose  to  the  end  of  the  purge  valve  and  im- 
merse its  other  end  in  a  pail  of  water.  If  it  is  air,  bubbles  will 
rise  to  the  surface,  while  if  it  is  ammonia,  it  will  be  absorbed  into 
the  water;  the  mingling  of  the  ammonia  with  the  water  will  cause 
a  crackling  sound,  and  the  temperature  of  the  water  will  increase 
owing  to  the  chemical  action. 

TESTING  AND  CHARGING. 

Having  described  the  different  parts  of  the  refrigerating  plant 
and  their  relations  to  one  another,  let  us  consider  the  process  of 
testing  and  charging,  or  introducing  the  ammonia  into  the  system. 
After  the  connections  are  made  between  the  different  parts,  whether 
the  system  is  brine  or  direct  expansion,  it  is  necessary  to  introduce 
air  pressure  into  it  to  determine  the  state  of  the  joints.  This  may 
be  done  in  sections  or  altogether.  It  is  customary,  however,  to  put 
a  higher  pressure  on  the  compression  side  of  the  plant  than  on  the 
evaporator  owing  to  the  difference  in  the  pressure  carried  in  opera- 
tion. Adjacent  to  each  compressor  is  placed  a  main  stop  valve,  on 
both  the  inlet  and  outlet  sides,  while  on  either  side  of  these  it  is 
customary  to  place  a  by-pass  or  purge  valve. 

Before  starting  the  compressor,  the  main  stop  valve  or  valves 
(if  there  be  two)  on  the  inlet  or  evaporating  side  of  the  compressor, 
is  closed,  the  small  valve  between  the  compressor  and  the  main 
stop  valve  opened,  and  all  of  the  other  valves  on  the  system  opened 
except  those  to  the  atmosphere.  The  compressor  may  then  be 
started  slowly,  air  being  taken  in  through  the  small  by-pass  valves 
and  compressed  into  the  entire  system.  It  is  well  to  raise  a  few 
pounds  pressure  on  the  entire  system,  before  admitting  water  into 
the  compressor  water  jackets  or  other  parts  of  the  system,  because 
if  a  joint  were  improperly  made  up,  it  would  be  possible  for  the 
water  to  enter  the  compressors,  or  coils  of  the  condenser  or  evap- 
orator, and  serious  damage  or  loss  of  efficiency  in  the  plant  occur 
which  it  might  be  impossible  to  locate  afterwards.  While  if  pres- 
sure exists  within  the  system  when  the  water  is  admitted,  ltd 


68  KEFKIGERATIOJST 

entrance  into  the  coils  or  system  is  impossible  while  the  pressure 
exists,  and  the  leak  is  at  once  visible,  and  may  be  remedied  before 
proceeding  farther. 

In  starting  the  test  it  is  also  well  to  try  the  two  pressure 
gauges  and  see  that  they  agree  as  to  graduation,  as  it  has  occurred 
that  owing  to  a  leakage  between  the  discharge  pipe  and  the  high 
pressure  gauge,  an  enormous  pressure  has  been  pumped  into  the 
system  causing  it  to  explode,  resulting  in  loss  of  life  and  property. 
If,  however,  the  pressures  are  found  to  be  equal  on  the  two  gauges 
it  is  safe  to  assume  that  they  are  recording  properly  and  their  con- 
nections  are  tight.  After  these  preliminaries  it  is  safe  to  put  an 
air  pressure  of  300  pounds  on  the  compression  side  of  the  plant, 
care  being  taken  to  operate  the  compressor  slowly,  not  raising  the 
temperature  of  the  compressed  air  too  much,  as  with  the  utmost 
care  in  making  up  joints  and  in  selecting  material,  certain  weak- 
nesses may  exist,  and  under  such  high  pressure  it  is  well  to  proceed 
with  caution. 

After  the  desired  pressure  has  been  reached,  the  entire  system 
should  be  gone  over  repeatedly  until  it  is  absolutely  certain  that  it 
is  tight.  Parts  which  can  be  covered  with  water,  such  as  a  sub- 
merged form  of  condenser  or  brine  tank  with  evaporating  coils, 
should  be  so  covered  that  the  entire  surface  may  be  gone  over  at  once 
and  with  almost  absolute  certainty.  The  slightest  leakage  will 
cause  air  bubbles  to  ascend  to  the  surface ;  they  may  be  traced  by 
allowing  the  water  to  flow  from  the  tank  while  the  air  pressure  is 
still  on  the  coils  or  system,  watching  the  points  wThere  it  stops  and 
marking  them,  to  be  taken  up  or  repaired  when  empty.  For  parts 
which  cannot  be  covered  with  water,  it  is  customary  to  apply  with 
a  brush  a  lather  of  such  consistency  that  it  will  not  run  off  too 
readily;  upon  coming  in  contact  with  a  leak,  soap  bubbles  are 
formed,  and  by  tracing  to  the  starting  point  the  leak  may  be  located. 
After  the  compression  system  has  been  subjected  to  a  pressure  of 
300  pounds  and  found  to  be  tight,  the  air  may  be  admitted  through 
the  liquid  ammonia  pipe  to  the  evaporating  side  of  the  plant,  care 
being  taken  that  the  pressure  does  not  rise  above  the  limit  of  the 
gauge  which  as  previously  stated  is  usually  120  pounds  and  the 
same  process  of  testing  as  applied  to  the  opposite  side  of  the  plant 
gone  over. 


KEFKIGERATION  69 


Many  engineers  require  the  vacuum  test  as  well  as  the  fore- 
going, and  although  if  the  former  is  gone  over  thoroughly,  there  can 
be  little  chance  of  leakage  afterwards,  it  is  better  to  be  over-exacting 
than  otherwise  in  the  matter  of  testing  and  preparation  of  the  plant, 
thus  preventing  the  possibility  of  leaks  that  may  prove  disas- 
trous. Open  the  main  stop  valves  on  the  inlet  line  and  close  the 
main  valves  above  the  compressor  on  the  discharge  line,  closing 
the  by-pass  valves  in  the  suction  line,  and  opening  those  in  the 
discharge  line  between  the  main  stop  valve  and  the  compressor. 
Have  all  the  other  valves  on  the  system  open  as  before  for  testing. 
Starting  the  compressor  draws  in  the  air  filling  the  system  through 
the  compressor  and  discharging  it  at  the  small  valve  left  open. 
Assuming  the  system  to  be  tight,  continuing  the  operation  will 
finally  exhaust  the  air  (or  nearly  so),  when  the  small  valves  should 
be  closed  and  the  pressure  gauges  watched  to  determine  whether  or 
not  leakage  exists. 

Assuming  that  the  system  and  apparatus  is  tight  in  every 
particular  and  that  it  is  otherwise  ready  to  be  placed  in  operation, 
we  are  now  ready  to  charge  the  ammonia  into  the  plant. 

If  the  air  has  been  exhausted  from  the  system  in  testing,  this 
usual  step  need  not  be  taken  before  charging,  and  it  is  only  neces- 
sary to  put  the  machine  in  proper  condition  to  resume  the  pump- 
ing of  the  gas,  and  attach  a  cylinder  of  ammonia  to  the  charging 
valve  to  enable  the  refrigeration  to  be  commenced.  The  main 
stop  valves  above  the  compressor  which  were  closed  in  expelling 
the  air  should  now  be  opened  and  by- pass  and  other  valves  to  the 
atmosphere  closed.  Close  the  outlet  valve  from  the  ammonia 
receiver  and  start  the  machine  slowly,  at  the  same  time  opening 
the  feed  valve  between  the  drum  of  ammonia  and  evaporator. 
The  anhydrous  liquid  ammonia  will  flow  into  the  evaporator 
through  the  regular  supply  pipe,  the  gas  resulting  from. evapora- 
tion being  taken  up  by  the  compressors  and  discharged  into  the 
condenser  and  finally  settling  down  into  the  receiver,  when  a 
sufficient  quantity  has  been  introduced  to  form  a  supply  there. 
Upon  closing  the  valves  between  the  drum  from  which  the  sup- 
ply is  being  drawn,  and  opening  the  outlet  valve  from  the  re- 
ceiver, the  process  of  refrigeration  by  the  compression  system  is 
regularly  in  operation. 


70  EEFKIGEBATION 


OPERATION  AND  MANAGEMENT  OF  THE  PLANT. 

Assuming  that  the  plant  has  been  properly  erected,  tested, 
and  charged  with  ammonia  of  a  good  quality,  and  (if  a  brine  system) 
with  brine  of  proper  strength  or  density,  as  already  explained,  it 
only  remains  to  keep  the  system  or  plant  in  that  condition.  As  all 
forms  of-  mechanism  are  liable  to  disarrangement  and  deterioration 
from  various  causes,  repairs  and  corrections  from  time  to  time 
must  be  made  to  keep  them  in  good  condition.  Let  us  now  consider 
the  most  important  points  requiring  attention. 

It  is  absolutely  necessary  for  the  good  working  of  any  type  of 
plant  or  apparatus  that  it  be  kept  clean.  As  a  steam  boiler  must 
be  clean  to  obtain  the  full  benefit  of  the  fuel  consumed,  so  must 
the  surfaces  of  the  condenser  and  evaporator  be  clean  to  obtain  the 
proper  results  from  the  condensing  water  and  evaporation  of  the 
ammonia  or  other  refrigerant. 

For  satisfactory  work  the  sjstem  should  be  purged  of  any 
foreign  element  present  in.  the  pipes,  such  as  air,  water,  oil,  or 
brine.  Foreign  matter  is  the  most  common  among  internal  causes 
for  loss  of  efficiency,  and  the  valved  openings  which  have  been 
shown  and  described  should  be  used  for  cleaning  the  system. 

Oil  is  used  as  a  lubricant  in  nearly  if  not  quite  all  compres- 
sors, and  the  quantity  should  be  the  least  amount  that  will  lubri- 
cate the  surfaces  and  prevent  undue  wear.  This  is  considerably 
less  than  the  average  engineer  is  inclined  to  think  necessary,  and 
consequently  a  coating  forms  on  the  walls  of  the  pipes  or  other 
surfaces  of  the  condensing  or  evaporating  systems,  and  a  propor- 
tionate decrease  in  the  duty  obtained.  It  is  also  necessary  that  the 
oil  be  of  such  a  nature  that  it  is  not  saponified  by  contact  with  the 
ammonia.  Such  a  change  would  choke  or  clog  the  pipes,  coating 
their  surfaces  with  a  thick  paste  which  causes  a  corresponding  loss 
as  the  amount  increases.  The  purge  valve  in  the  bottom,  of  the  oil 
interceptor  may  be  opened  slightly  about  once  each  week,  and  the 
oil  discharged  from  the  compressors  drawn  off  into  a  pail  or  can, 
unless  a  blow-off  reservoir  is  provided.  After  the  gas  with  which 
it  is  charged  has  escaped,  the  oil  should  be  practically  the  same  as 
when  fed  into  the  compressors.  If,  however,  the  oil  is  not  of  the 
proper  quality  it  will  remain  thick  and. pasty,  or  gummy,  showing 


EEFKIGEKATIOJT  71 


;t  to  have  been  affected  by  the  ammonia.     Its  use  should  not  be 

continued. 

By  opening  the  purge  valves,  which  are  usually  provided  at 
the  bottom  manifold  or  header  of  the  brine  tank  and  the  bottom 
head  of  the  brine  cooler,  oil  or  water,  if  any  be  in  that  part  of  the 
system,  may  be  drawn  off.  These  valves,  however,  should  not  be 
opened  unless  there  is  some  pressure  in  that  part  of  the  system,  as 
air  would  be  admitted  if  the  pressure  within  the  apparatus  is 
below  that  of  the  atmosphere.  Air  may  enter  the  system  through 
a  variety  of  causes  and  its  presence  is  attended  with  higher  con- 
den  sing  pressure  and  a  falling  off  in  the  amount  of  work  performed. 
For  the  removal  of  air  from  the  apparatus  a  purge  valve  is  placed 
at  the  highest  point  in  the  condenser  or  discharge  pipe  from  the 
compressors  near  the  condenser,  which  may  be  tried  when  the 
presence  of  air  or  foreign  gases  is  suspected.  This  should  be  done 
after  the  compressor  has  been  stopped.  When  the  condenser  has 
fully  cooled  and  the  gases  separated,  a  small  rubber  hose  or  pipe 
may  be  carried  into  a  pail  of  water  and  the  purge  Valve  or  valves 
slightly  opened.  If  air  or  other  gases  exist  in  the  system  bubbles 
will  rise  to  the  surface  of  the  water  so  long  as  it  is  escaping,  while, 
if  ammonia  is  being  blown  off,  it  will  be  absorbed  in  the  water 
and  not  rise  to  the  surface. 

To  prevent  the  possibility  of  air  getting  into  the  system,  the 
evaporating  pressure  should  never  be  brought  below  that  of  the 
atmospheric,  or  0°  on  the  gauge,  as  at  such  times,  with  the  least 
leakage  at  any  point,  it  is  sure  to  enter.  Should  it  become  neces- 
sary to  reduce  the  pressure  below  that  point,  it  is  well  first  to 
tighten  the  compressor  stuffing  boxes  and  allow  the  pressure  to 
remain  below  0°  only  the  shortest  possible  time  as  not  only  air 
may  enter,  but  if  it  be  ,the  brine  system  and  a  leak  exists,  brine 
also  will  be  drawn  in. 

From  the  foregoing  it  is  evident  that  in  order  to  obtain  satis- 
factory results,  the  interior  of  the  system  must  be  kept  clean  by 
purging  at  the  different  points  provided  for  this  purpose;  and  it 
need  only  be  added  in  this  connection,  that  when  the  presence  of. 
oil  or  moisture  becomes  apparent  in  any  quantity,  the  coils  or 
other  parts  should  be  disconnected  and  blown  out  with  steam 
until  thoroughly  clean  and  afterwards  with  air  to  make  certain 


72  EEFKIGEEATIOK 


that  condensation  from  the  steam  does  not  remain,  arter  which  the 
parts  may  again  be  connected  and  tested  ready  for  operation. 

If  the  plant  be  a  brine  system  it  is  necessary  that  the  brine 
be  maintained  at  a  proper  strength  or  density  to  obtain  satisfac- 
tory results,  for  if  it  becomes  weakened  it  freezes  on  the  surfaces 
of  the  pipes  or  evaporator,  acting  as  an  insulator  and  preventing 
the  rapid  transmission  of  heat  through  the  walls. 

Frequently  the  engineers  or  owners  in  looking  about  for  the 
cause  of  a  falling  off  in  the  capacity  of  a  plant,  overlook  the  fact 
that  the  strength  of  the  brine  is  the  sole  difficulty,  and  the  addi- 
tion of  salt  or  chloride  of  calcium  is  a  remedy.  Referring  to  the 
tables  of  brine  solutions,  there  should  be  no  difficulty  in  determin- 
ing  the  proper  strength  of  the  brine  for  the  different  temperatures 
at  which  the  plant  may  be  operating;  but  as  already  stated,  this 
should  be  made  to  correspond  to  the  temperature  of  the  evaporat- 
ing ammonia  rather  than  the  temperature  at  which  the  brine  may 
be  handled. 

It  is  of  great  importance  to  know  at  all  times  whether  or  not 
the  gas  taken  into  the  compressors  is  fully  discharged  into  the 
condenser,  aa  the  slightest  loss  at  this  point  is  certain  to  make 
itself  felt  in  the  operation  of  the  plant.  The  compressor  or  valves 
seldom  need  be  taken  apart  to  determine  their  operation.  The 
engineer  should  be  able  to  discern  the  slightest  change  in  tem- 
perature from  the  normal,  when  the  compressors  are  working  at 
their  best,  by  placing  the  hand  on  the  inlet  and  outlet  pipes  or  the 
lower  part  of  the  compressors.  Should  the  inlet  pipe  to  one  com- 
pressor be  warmer  than  that  to  the  other  (of  a  pair),  or  the  frost  on 
the  pipe  from  the  evaporator  reach  nearer  one  compressor  than  the 
other,  it  is  then  certain  that  the  one  with  the  higher  temperature, 
or  from  which  the  frost  is  farthest,  is  not  working  properly  or 
doing  as  much  duty  as  the  other,  and  it  is  equally  certain  that 
some  condition  exists  which  prevents  the  complete  filling  and  dis- 
charge of  its  contents;  possibly  it  has  more  clearance  or  leaky 
valves. 

The  most  common  difficulties  experienced  with  ammonia  con- 
densers  are  those  of  keeping  the  external  surfaces  clean  and  free 
from  deposits,  and  preventing  the  accumulation  of  air  or  foreign 
gases  within.  Deposits  on  the  surface  are  usually  of  two  kinds,  one 


REFEIGEEATION  73 


which  remains  soft  and  may  be  washed  off  with  a  brush  or  wire 
scraper  such  as  is  used  for  cleaning  castings  in  a  foundry,  the  other 
a  hard  deposit  which  must  be  loosened  with  a  hammer  or  scraper.  It 
is  hardly  necessary  to  explain  in  detail  the  methods  employed  in 
cleaning  the  condenser  as  this  is  a  matter  that  each  engineer  will  be 
able  to  accomplish  in  his  own  way.  It  should  not,  however,  be 
overlooked,  and  with  a  condensing  pressure  higher  than  ordinary, 
this  should  be  the  first  point  to  be  examined  after  the  water  supply. 

Air,  or  foreign  gases  due  to  decomposition  of  the  ammonia  or 
other  causes  find  their  way  into  the  condenser  and  make  them- 
selves  manifest  generally  in  a  higher  condensing  pressure,  or  a 
falling  off  in  the  duty  to  be  obtained  from  the  plant.  They  should 
be  blown  off  through  the  purge  ^alve  at  the  top  of  the  condenser 
in  the  manner  already  described. 

It  is  possible,  through  leakage  of^the  coils  or  other  parts  of  the 
apparatus,  that  the  ammonia  may  become  mixed  with  brine  or 
water,  thereby  retarding  its  evaporation  and  interfering  with  the 
proper  or  usual  operation  of  the  plant.  If  this  is  suspected,  a 
sample  may  be  drawn  off  into  a  test  glass  through  the  charging 
valve  or  purge  valve  of  the  brine  tank  or  ammonia  receiver,  and 
allowed  to  evaporate,  in  which  case  the  water  or  brine  will  remain 
in  the  glass  and  the  relative  amount  be  determined.  Through 
careful  evaporation,  and  continued  purging  of  the  evaporator  at 
intervals,  this  may  in  time  be  eliminated,  and  care  should  be 
taken  to  prevent  future  recurrence. 

Loss  of  ammonia  should  be  constantly  guarded  against.  It  is 
watchfulness  which  determines  between  a  wasteful  and  an  econom- 
ical plant  in  this  particular,  and  the  engineer  who  allows  the 
slightest  smell  of  ammonia  to  exist  about  the  plant  is  certain  to  be 
confronted  with  excessive  ammonia  bills;  while  he  who  is  constantly 
on  the  alert  and  never  rests  until  his  plant  is  as  free  from  the 
smell  of  ammonia  as  an  ordinary  engine  room,  will  be  referred  to 
as  the  one  who  ran  such  and  such  a  plant  without  addition  of  more 
ammonia  for  so  many  years. 

The  escape  of  ammonia  into  the  atmosphere  is  readily  de- 
tected; but  where  a  leakage  occurs  in  a  submerged  condenser, 
brine  tank  or  brine  cooler  it  is  necessary  to  examine  the  surround- 
ing  liquid  to  determine  whether  or  not  it  exists.  For  this  purpose 


74  REFRIGERATION 

various  agents  are  employed,  and  may  be  obtained  of  druggists  or 
from  the  manufacturers  of  ammonia.  Red  Litmus  paper  when 
dipped  into  water  or  brine  contaminated  with  ammonia  will  turn 
blue.  Nessler's  solution  causes  the  affected  water  to  turn  yellow 
and  brown,  while  Phenolphthalen  causes  a  bright  pink  color  with 
the  slightest  amount  of  ammonia  present. 

The  stopping  of  a  leakage  of  ammonia  in  the  brine  tank  or 
cooler  may  be  possible  while  the  plant  is  in  operation,  by  shutting 
off  the  coil  in  which  it  occurs,  or,  if  the  point  is  accessible  a 
clamp  and  gasket  may  be  put  in  place  temporarily. 

PROPORTION  BETWEEN  THE  PARTS  OF  A  REFRIGER- 
ATING PLANT. 

There  is  necessarily  a  certain  ratio  or  proportion  between  the 
several  parts  of  a  refrigerating  plant,  as  there  is  between  the 
boiler,  engine,  and  parts  of  a  steam  or  power  plant,  in  order  to 
obtain  the  most  economical  results.  It  is  first  necessary  that  the 
evaporator  be  provided  with  heat-transmitting  surface  sufficient  to 
conduct  284,000  B.  T.  U.  from  the  brine  to  the  ammonia,  for 
each  ton  of  refrigeration  to  be  performed.  "Without  going  into  a 
theoretical  calculation  of  this  amount,  we  shall  state  in  both  lineal 
feet  of  pipe  and  square  feet  of  pipe  surface  the  commercial  sizes 
and  amounts  ordinarily  in  use. 

The  coil  surface  in  a  brine-tank  system  of  refrigeration,  should 
contain  approximately  50  square  feet  of  external  pipe  surface,  to 
each  ton  in  refrigerating  capacity  of  the  plant,  when  it  is  to  be 
operated  at  a  temperature  of  15°  Fahr.  This  is  an  ample  allow- 
ance and  will  be  found  under  general  working  conditions  to  give 
readily  the  required  capacity.  While  tests  have  been  made  in 
which  40  square  feet  of  pipe  surface  has  been  found  sufficient  for 
one  ton  of  refrigeration,  it  will  be  safer  to  use  the  former  amount, 
owing  to  the  varied  conditions  under  which  a  plant  may  be  oper- 
ated. This  would  amount  in  round  figures  to  150  linear  feet  of 
1-inch  pipe,  115  feet  of  IJ-inch,  100  feet  of  l-|-inch,  or  80  feet  of 
2-inch  pipe. 

The  brine  tank  should  contain  from  40  to  GO  cubic  feet  (de- 
pending  on  the  amount  of  storage  capacity  desired)  for  each  ton  in 
capacity  of  the  plant.  The  brine  cooler  should  contain  12  square 


REFKIGEKATIOff  75 


feet  of  external  pipe  surface  for  each  ton,  from  which,  in  comparison 
with  the  amount  required  for  the  brine- tank  system,  the  statements 
regarding  the  relative  efficiency  of  the  two  methods  of  cooling  brine 
may  be  more  readily  understood.  This  amount  of  surface  would 
practically  correspond  to  35  linear  feet  of  1-inch  pipe,  28  feet  of 
ll-inch,  25  feet  of  IJ-inch  or  19  feet  of  2-inch  pipe.  The  shell  of 
the  cooler  is  made  sufficiently  large  to  contain  only  the  number  of 
coils  necessary,  there  being  no  advantage  in  a  larger  shell. 

The  submerged  type  of  ammonia  condenser  should  contain 
approximately  85  square  feet  of  external  surface  which  nearly  cor. 
responds  to  100  linear  feet  of  1-inch  pipe,  80  feet  of  IJ-inch,  70  feet 
of  IJ-inch  and  56  feet  of  2-inch  pipe. 

The  atmospheric  type  of  condenser  should  contain  30  square 
feet  of  external  pipe  surface  which  corresponds  to  87  linear  feet 
of  1-inch  pipe,  69  feet  of  l|-inch,  60  feet  of  l|-inch  and  48  feet 
of  2-inch  pipe. 

The  double-pipe  type  of  condenser,  as  usually  rated,  contains 
7  square  feet  of  external  pipe  surface  for  the  water  circulating  pipe 
and  about  10  square  feet  of  internal  surface  of  the  outer  pipe  and 
corresponds  to  approximately  20  linear  feet  each  of  1^-inch  and 
2 -inch  sizes  for  each  ton  of  refrigerating  capacity. 

The  above  quantities  are  based  on  a  water  supply  of  average 
temperature  (60°)  and  quantity.  In  cases  of  a  limited  supply  or 
higher  temperature  than  ordinary,  a  greater  amount  should  be  used. 

The  ammonia  compressor  should  be  of  such  dimensions  that 
it  will  take  away  the  gas  from  the  brine  cooler,  evaporating  coils, 
or  system,  as  rapidly  as  formed  by  the  evaporation  of  the  liquid 
ammonia,  and  unless  the  temperature  at  which  the  plant  is  to  be 
operated  be  known,  it  is  impossible  to  determine  the  volume  of 
gas  to  be  handled  and  the  necessary  sizes  of  the  compressor. 

As  stated  before,  the  unit  of  a  refrigerating  plant  is  usually 
expressed  in  tons  of  refrigeration  equal  to  284,000  B.  T.  U.  Up 
to  the  present  time,  however,  a  standard  temperature  at  which 
this  duty  shall  be  performed  has  never  been  established,  and 
therefore  the  rating  of  a  machine,  evaporator,  or  condenser  by 
tonnage  is  a  merely  nominal  one  and  misleading  to  the  purchaser, 
a  range  of  as  great  as  50  per  cent  very  often  existing  in  the 
tenders  for  certain  contracts.  Upon  the  basis,  however,  of  the 


76  REFRIGERATION 


average  temperature  required  of  the  refrigerating  apparatus  that 
of  15°  Fahr.  is  probably  the  mean;  and  at  this  temperature  in  the 
outgoing  brine,  it  is  necessary  to  take  away  from  the  evaporator 
nearly  7,000  cubic  inches  of  gas  per  minute  for  each  tori  of 
refrigeration  developed  in  twenty-four  hours.  This  may  be  con- 
sidered  as  a  fair  basis  for  the  rating  of  the  displacement  of  the 
compressor  or  compressors  of  the  plant,  unless  a  specific  tempera- 
ture is  stated  at  which  the  plant  is  to  operate.  At  0°  Fahr.  it  is 
necessary  to  calculate  on  approximately  9,000  cubic  inches,  while 
At  28°  Fahr.  about  5,000  will  be  the  required  amount. 

For  example,  if  we  have  two  single  acting  compressors  12 
inches  diameter  by  24  inches  stroke  operating  at  70  revolutions 
per  minute,  we  would  have  113.09  (inches,  area  of  12-inch  circle) 
X  24  (inches  stroke)  X  2  (number  of  compressors)  X  70  (revolu- 
tions)  -r-  7,000  (cubic  inches  displacement  required)  =  54.28  (tons 
refrigeration  per  24  hours  of  operation),  while  if  the  same  machine 
is  to  be  operated  at  or  near  a  temperature  of  zero  and  we 
divide  the  product  by  9,000  we  have  a  capacity  of  42.22  tons  only 
in  the  same  length  of  time.  The  above  quantities  are  given  as 
approximate  only,  but  they  have  been  deduced  from  the  average 
results  obtained  from  years  of  practice  and  will  be  found  reliable 
under  average  conditions.  It  is  to  be  hoped,  however,  that  a 
standard  will  soon  be  adopted  which  will  rate  machines  or  plants 
by  cubic  inches  displacement  at  a  certain  number  of  revolutions 
or  a  stated  piston  speed,  and  the  cooling  of  a  certain  number  of 
gallons  of  brine  per  minute  through  a  certain  range  of  tern- 
perature. 


KEFKIGEKATION 


77 


THERMOMETER  SCALES. 


Fahr. 

Cent. 

Reau. 

Fahr. 

Cent. 

Reau. 

Fahr. 

Cent. 

Reau. 

212 

100 

80 

120 

48.9 

39.1 

30 

—  1.1 

—  0.9 

210 

-  98.9 

79.1 

118 

47.8 

38.2 

28 

—  2.2 

—  1.8 

208 

97.8 

78.2 

116 

46.7 

37.3 

26 

—  3.3 

—  2.7 

206 

96.7 

77.3 

114 

45.6 

36.4 

24 

—  4.4 

—  3.6 

204 

95.6 

76.4 

112 

44.4 

35.6 

22 

—  56 

—  4.4 

202 

94.4 

75.6 

110 

43.3 

34.7 

20 

—  67 

—  5.3 

200 

93.3 

74.7 

108 

42.2 

33.8 

18 

—  7.8 

—  6.2 

198 

92.2 

73.8 

106 

41.1 

32.9 

16 

—  8.9 

—  7.1 

196 

91.1 

72.9 

104 

40 

32 

14 

—10 

—  8 

194 

90 

72 

102 

38.9 

31.1 

12 

—11.1 

—  89 

192 

88.9 

71.1 

100 

37.8 

30.2 

10 

12.2 

—  9.8 

190 

87.8 

70.2 

98 

36.7 

29.3 

8 

—13.3 

—10.7 

188 

86.7 

69.3 

96 

35.6 

28.4 

6 

—44.4 

—11.6 

186 

85.6 

68.4 

94 

34.4 

27.6 

4 

—15.6 

—12.4 

184 

84.4 

67.6 

92 

33.3 

26'.  7 

2 

—167 

—13.3 

182 

83.3 

66.7 

90 

32.2 

25.8 

0 

—17.8 

—142 

180 

82.2 

65.8 

88 

31.1 

24.9 

—  2 

—18.9 

—15.1 

178 

81.1 

64.9 

86 

30 

24 

—  4 

—20 

—16 

176 

80 

64 

84 

28.9 

23.1 

—  6 

—21.1 

—16.9 

174 

78.9 

63.1 

82 

27.8 

222 

—  8 

—22.2 

—17.8 

172 

77.8 

62.2 

80 

267 

21.3 

—10 

—233 

—18.7 

170 

76.7 

61.3 

78 

25.6 

20.4 

—12 

—24.4 

—19.6 

168 

75.6 

60.4 

76 

24.4 

19.6 

—14 

—25.6 

—20.4 

166 

74.4 

59.6 

74 

23.3 

18.7 

—16 

—26.7 

—21.3 

164 

73.3 

58.7 

72 

22.2 

17.8 

—18 

—27.8 

—22.2 

162 

72.2 

57.8 

.  70 

21.1 

16.9 

—20 

—28.9 

—23.1 

160 

71.1 

56.9 

68 

20 

1.6 

—22 

—30 

—24 

158 

70 

56 

66 

18.9 

15.1 

—24 

—31.1 

—249 

156 

68.9 

55.1 

64 

17.8 

14.2 

—26 

—32.2 

—25.8 

154 

67.8 

54.2 

62 

16.7 

13.3 

—28 

—333 

—26.7 

152 

66.7 

53.3 

60 

15.6 

12.4 

—30 

—34.4 

—27.6 

150 

65.6 

52.4 

58 

14.4 

11.6 

—32 

—35.6 

—28.4 

148 

64.4 

51.6 

56 

13.3 

10.7 

—34 

—36.7 

—29.3 

146 

63.3 

50.7 

54 

12.2 

9.8 

—36 

—  37.8 

—30.2 

144 

62.2 

49.8 

52 

11.1 

8.9 

—38 

—38.9 

—31.1 

142 

61.1 

48.9 

50 

10 

8 

—40 

—40 

—32 

140 

60 

48 

48 

8.9 

7.1 

—42 

—411 

—32.9 

138 

58.9 

47.1 

46 

7.8 

6.2 

—44. 

—42.2 

—33.8 

136 

57.8 

46.2 

44 

6.7 

5.3 

—46 

—43.3 

—347 

134 

56.7 

45.3 

42 

5.6 

4.4 

—48 

—44.4 

—35.6 

132 

55.6 

44.4 

40 

4.4 

3.6 

—50 

—45.6 

—36.4 

130 

54.4 

43.6 

38 

3.3 

2.7 

—52 

—46.7 

—373 

128 

53.3 

42.7 

36 

2.2 

1.8 

—54 

—47.8 

—38.2 

126 

52.2 

41.8 

34 

.1.1 

0.9 

—56 

—48.9 

—39.1 

124 

51.1 

40.9 

32 

0 

0 

—58 

—50 

—40 

122 

50 

40 

78 


EEFKIGEEATIOK 


TEMPERATURE,  PRESSURE,  LATENT  HEAT  AND  WEIGHT  OF  AMMONIA, 
OR  PROPERTIES  OF  SATURATED  AMMONIA. 


Temp. 

Pres 

sure 

Latent 

TJtvo  4- 

Volume  in 
Cu.  Ft.  of 

Volume  in 
Cu.  Ft.  of 

Weight  of 
1  Cu.  Ft. 

F. 

Absolute 

Gauge 

xieat 

1  Lb.  Vapor 

1  Lb.  Liquid 

Vapor 

—40 

10.69 

—4.01 

579.67 

24.38 

.0234 

.0411 

—35 

12.31 

—2.39 

576.69 

21.32 

.0236 

.0471 

—30 

14.13 

—  .57 

573.69 

18.69 

.0237 

.0535 

—25 

16.17 

1.47 

570.68 

16.44 

.0238 

.0609 

—20 

18.45 

3.75 

567.67 

1448 

.024 

.069 

—15 

20.99 

6.29 

564.64 

12.81 

.0242 

.0775 

—10 

23.77 

9.07 

56161 

11.36 

.0243 

.088 

—  5 

27.57 

12.87 

558.56 

9.89 

.0244 

.1011 

0 

30.37 

15.67 

555.5 

9.14 

.0246 

.1094 

+  5 

34.17 

19.47 

552.43 

8.04 

.0247 

.1243 

10 

38.55 

23.85 

549.35 

7.2 

.0249 

.1381 

15 

42.93 

28.23 

546.26 

6.46 

.025 

.1547 

20 

47.95 

33.25 

543  15 

5.82 

.0252 

.1721 

25 

53.43 

38.73 

540.03 

5.24 

.0253 

.1908 

30 

59.41 

44.71 

536.92 

4.73 

.0254 

.2111 

35 

65.93 

51.23 

533.78 

4.28 

.0256 

.2336 

40 

73. 

58.3 

530.63 

3.88 

.0257 

.2577 

45 

80.66 

65.96 

527.47 

353 

.026 

.2832 

50 

88.96 

74.26 

524.3 

3.21 

.02601 

.3115 

55 

97.63 

82.93 

521.12 

2.93 

.02603 

.3412 

60 

107.6 

92.9 

517.93 

2.67 

.0265 

.3745 

65 

118.03 

103.33 

515.33 

2.45 

.0266 

.4081 

70 

129.21 

114.51 

511.52 

224 

.0268 

.4664 

75 

144.25 

12655 

508.29 

2.05 

.027 

.4978 

80 

154.11 

139.41 

50466 

1.89 

.0272 

.5291 

85 

167.86 

153.16 

501.81 

.74 

.0273 

.5747 

90 

182.8 

168.1 

498.11 

.61 

.0274 

.6211 

95 

198.37 

183.67 

495.29 

.48 

.0277 

.6756 

100 

215.14 

200.44 

491.5 

.36 

.0279 

.7353 

105 

232.98 

218.28 

488.72 

.29 

.0281 

.7862 

110 

251.97 

237.27 

485.42 

.2 

.0283 

.8451 

115 

272.14 

257.44 

482.41 

.12 

.0285 

.9042 

120 

293.49 

278.79 

47879 

.04 

.0287 

.9738 

125 

316.16 

301.'  46 

475.45 

.97 

.0289 

1.172 

130 

340.42 

325.72 

472.11 

.9 

.0291 

1.2218 

135 

365.16 

350.46 

468.75 

.84 

.0293 

1.3212 

140 

392.22 

377.52 

465.39 

.79 

.0295 

1.4108 

145 

420.49 

405.79 

462.01 

.74 

.0297 

1.4904 

150 

450.2 

435.5 

458.62 

.69 

.0299 

1.5896 

KEFEIGEEATION 


79 


TABLE  OF  CALCIUM  BRINE  SOLUTION. 


Deg. 
Baum6 
60°  F. 

Deg. 
Salom- 
eter. 
60°  F. 

Per  Cent 
Calcium 
by  Weight 

Lbs.  per 
Cu.  Ft. 
Sol. 

Lbs. 
per 
Gallon 

Specific 
Gravity 

Specific 
Heat 

Freezing 
Point  F. 

Amm. 
Gauge 
Pressure 

0 

0 

0 

0 

0 

1 

1 

32 

47.31 

1 

4 

.943 

1.25 

i 

1.007 

.996 

31.1 

46.14 

2 

8 

1.886 

2.5 

i 

1.014 

.988 

30.33 

45.14 

3 

12 

2.829 

3.75 

1.021 

.98 

29.48 

44.06 

4 

16 

3.772 

5 

i* 

1.028 

.972 

28.58 

43 

5 

20 

4.715 

6.25 

i 

1.036 

.964 

27.82 

42.08 

6 

24 

5.658 

7.5 

i 

1.043 

.955 

27.05 

41.17 

7 

28 

6.601 

8.75 

if 

1.051 

.946 

26.28 

40.25 

8 

32 

7.544 

10 

i* 

1.058 

.936 

25.52 

39.35 

9 

36 

8.487 

11  25 

if 

1.066 

.925 

24.26 

37.9 

10 

40 

9.43 

12.5 

ii 

1.074 

.911 

22.8 

36.3 

11 

44 

10.373 

13.75 

it 

1.082 

.896 

21.3 

34.67 

12 

48 

11.316 

15 

2 

1.09 

.89 

19.7 

32.93 

13 

52 

12.259 

16.25 

*k 

1.098 

.884 

18.1 

31.33 

14 

56 

13202 

17.5 

2* 

1.107 

.878 

16.61 

29.63 

15 

60 

14.145 

18.75 

1ft 

1.115 

.872 

15.14 

28.35 

16 

64 

15.088 

20 

8| 

1.124 

.866 

13.67 

27.04 

17 

68 

16031 

21.25 

21 

1.133 

.86 

12.2 

25.76 

18 

72 

16.974 

22.5 

3 

1.142 

.854 

10 

23.85 

19 

76 

17.917 

23.75 

8* 

1.151 

.849 

7.5 

21.8 

20 

80 

18.86 

25 

3* 

1.16 

.844 

4.6 

19.43 

21 

84 

19.803 

26.25 

3| 

1.169 

.839 

1.7 

17.06 

22 

88 

20.746 

27.5 

8f 

1.179 

.834 

—  1.4 

14.7 

23 

92 

21.689 

28.75 

3f 

1.188 

.825 

—  4.9 

12.2 

24 

96 

22.632 

30 

4 

1.198 

.817 

—  8.6 

9.96 

25 

100 

23.575 

31.25 

41 

1.208 

.808 

—11.6 

8.19 

26 

24.518 

32.5 

4* 

1.218 

.799 

—17.1 

5.22 

27 

25.461 

33.75 

H 

1.229 

.79 

—21.8 

2.94 

28 

26.404 

35 

4| 

1.239 

.778 

—27. 

.65 

29 

27.347 

36.25 

4f 

1.25 

.769 

—32.6 

l"Vao 

30 

28.29 

37.5 

5 

1.261 

.757 

—39.2 

8.5"" 

31 

29.233 

38.75 

5£ 

1.272 

—46.3 

12 

32 

30.176 

40 

5^ 

1.283 

—54.4 

15 

33 

31.119 

41.25 

5| 

1.295 

—52.5 

10 

34 

32.062 

42.5 

H 

1.306 

—39.2 

4 

35 

33 

43.75 

5f 

1.318 

—25.2 

1.5 

80 


EEFKIGEKATION 


TABLE  OP  CHLORIDE  OF  SODIUM  (SALT)  BRINE. 


Degrees 
on 
Salom. 

Percent- 
age Salt 
by  Weight 

Pounds 
Salt  per 
Cu.  Ft. 

Pounds 
Salt  per 
Gallon 

Specific 
Gravity 

Specific 
Heat 

Freezing 
Point  F. 

Ammonia 
Gauge 
Pressure 

0 

0 

0 

0 

1 

1 

32 

47.32 

5 

1.25 

.785 

.105 

1.009 

.99 

30.3 

45.1 

10 

2.5 

1.586 

.212 

1.0181 

.98 

28.6 

43.03 

15 

3.75 

2.401 

.321 

1.0271 

.97 

26.9 

41 

20 

5 

3.239 

.433 

1.0362 

.96 

25.2 

38.96 

25 

6.25 

4.099 

.548 

1.0455 

.943 

23.6 

37.19 

30 

7.5 

4.967 

.664 

1.0547 

.926 

22 

35.44 

35 

8.75 

5.834 

.   .78 

1.064 

.909 

20.4 

33.69 

40 

10 

6.709 

.897 

1.0733 

.892 

18.7 

31.93 

45 

11.25 

7.622 

1.019 

1.0828 

.883 

17.1 

30.38 

50 

12.5 

8.542 

1.142 

.0923 

.874 

15.5 

28.73 

55 

13.75 

9.462 

1.265 

.1018 

.864 

13.9 

27.24 

60 

15 

10.389 

1.389 

.1114 

.855 

12.2 

25.76 

65 

16:25 

11.384 

1.522 

.1213 

.848 

10.7 

24.46 

70 

17.5 

12.387 

1.656 

.1312 

.842 

9.2 

23.16 

75 

18.75 

13.396 

1.791 

.1411 

.835 

7.7 

21.82 

80 

20 

14.421 

1.928 

1.1511 

.829 

6.1 

20.43 

85 

21.25 

15.461 

2.067 

1.1614 

.818 

4.6 

19.16 

90 

22.5 

16.508 

2.207 

1.1717 

.806 

3.1 

18.2 

95 

23.75 

17.555 

2.347 

1.182 

.795 

1.6 

16.88 

100 

25 

18.61 

2.488 

1.1923 

.783 

0 

15.67 

gs 

§£ 

0- 


REFRIGERATION 

PART  II 


REFRIGERATION  BY  CARBONIC  ANHYDRIDE  GAS. 

In  general  design  and  requirements,  the  refrigerating  ma- 
chine using  carbonic  anhydride  gas  is  substantially  like  the  ma- 
chine using"  ether,  ammonia,  or  carbonic  dioxide  gases  in  that  it 
liquefies  the  gas  by  the  removal  of  the  latent  heat  in  condensers 
and  tanks.  Where  it  differs  materially  is  in  the  pressures  required 
to  accomplish  the  liquefaction  of  the  gas. 

The  following  table  shows  the  pressure  required  for  lique- 
faction at  different  temperatures  from  an  approximate  normal 
condition,  of  80  degrees  to  a  point  where  the  gas  remains  a  liquid 
under  the  atmospheric  pressure  of  14.7  pounds  from  the  absolute. 

TEMPERATURE  OF  GAS  LIQUEFIED. 


Temperature 
Fahrenheit. 

Pressure 
Pounds  per  sq.  in. 

Temperature 
Fahrenheit. 

Pressure 
Pounds  per  sq.  in. 

80 

1000.6 

-60 

134.2 

70 

889.3 

-70 

113.2 

60 

771.7 

-80 

96.2 

50 

689.4 

-90 

81.0 

40 

588.0 

-100 

70.1 

30 

507.1 

-110 

57.9 

20 

433.6 

-120 

47.4 

10 

367.1 

-130 

38.4 

0 

311.6 

-140 

30.0 

-10 

260.1 

-150 

21.3 

-20 

217.5 

-160 

15.2 

-30 

182  8 

-170 

7.1 

-40 

162.8 

-179.6 

0.0 

-50 

156.8 

In  the  operation  of  refrigerating  machines  where  the  gas  is 
rapidly  passing  through  the  condensers,  it  has  been  established 
that  the  temperature  of.  the  gas  liquefied  is  from  8  to  12  degrees 
above  that  of  the  water  used  for  condensing.  If  the  condensing 
water  is  60  degrees,  though  during  the  summer  days  of  August 


KEFRIGEKATION  83 

or  September  a  temper  atiire  of  65  to  76  degrees  is  more  common 
where  city  service  water  is  in  use,  a  pressure  of  at  least  1,000 
pounds  per  square  inch  is  required  for  the  working  conditions. 

With  this  pressure,  compressing  cylinders  and  piping  must 
be  very  strong  to  withstand  the  pressure,  and  the  diameter  of  the 
gas  cylinder  must  be  small  compared  with  that  of  the  steam 
cylinder.  As  carbonic  anhydride  gas  does  not  attack  copper  or 
kindred  metals  they  can  be  used  with  safety  for  the  working  parts 
of  the  machine. 

Although  as  dangerous  as  any  of  the  other  gases,  as  it  excludes 
the  presence  of  oxygen,  the  gas  is  not  noticed  by  smell  as  is  the 
case  with  ammonia.  In  a  vapor  form,  the  specific  gravity  is 
greater  than  that  of  the  atmosphere,  and  the  gas  escaping  in  small 
quantities  is  not  easily  detected  as  it  immediately  sinks  in  the 
cellars,  sewers,  or  loose  earth.  As  life  cannot  be  sustained  without 
the  presence  of  oxygen,  any  gas  that  excludes  it  is  dangerous.  The 
presence  of  ammonia  is  so  pronounced  that  it  is  easily  detected 
when  but  a  small  amount  is  in  the  atmosphere,  while  the  presence 
of  carbonic  anhydride  gas  is  difficult  to  detect  even  up  to  the 
moment  of  exhaustion  of  life. 

In  the  use  of  carbonic  anhydride  gas  it  is  necessary  that  the 
most  careful  attention  be  paid  to  the  joints  and  stuffing  boxes.  The 
compressors  are  invariably  of  the  single-acting  type,  as  it  is  almost 
impossible  to  maintain  tight  stuffing  boxes  under  the  intense  pres- 
sure necessary  for  liquefaction 

Compressors  are  quite  extensively  made  for  the  liquefaction 
of  carbonic  acid  anhydride  gas,  by  industries  supplying  the  same 
in  small  carboys  of  steel  for  recharging  soda  water  or  beer,  or  any 
beverage  which  requires  the  addition  of  carbonic  acid  gas  for 
enlivenment.  In  the  better  class  of  these  compressors,  the  cylin- 
der for  compressing  the  gas  is  compounded  as  shown  in  Fig.  46. 
By  this  design  the  first  set  of  cylinders  deliver  the  gas  to  a  re- 
ceiver at  a  pressure  between  400  and  600  pounds  per  square  inch. 
Here  the  gas  is  cooled ;  from  this  cylinder  the  suction  of  the  final 
pump  is  taken,  which  leaves  the  gas  at  1,000  pounds  pressure. 
There  is  an  advantage  in  machines  of  this  build  (compound  cylin- 
ders), as  there  is  a  less  amount  of  engine  friction  than  in  single- 
acting  cylinders. 

Fig.  47  shows  a  single-acting  horizontal  compressing  cylinder 
direct  connected  to  a  throttling  steam  engine  "D"  valve  pattern, 


REFRIGERATION 


EEFHIGERATION 


85 


FIG.  48 
DIRECT- CONNECTED  VERTICAL  REFRIGERATING  COMPRESSOR 


KEFRIGEKATION 


double  cylinder  operating  on  a  single  shaft.  The  tail  rod  of  the 
steam  cylinder  extends  into  and  forms  the  piston  rod  of  the  com- 
pressor. 

Fig.  48  shows  a  vertical  stearn  engine  connected  to  a  single- 


FIG.  49 
BELT- DRIVEN  REFRIGERATING  COMPRESSOR 

acting  compressor ;  the  compressor  being  bolted  to  the  side  of  the 
steam  cylinder  with  a  double  center-crank  engine  and  over-hung 
fly  wheel. 

Fig.  49  shows  a  single-acting  vertical  compressor,  connected 


REFRIGERATION  87 


to  a  shaft  and  belt,  wheels  over  hanging.     This  design  is  for  a  belt- 
driven  plant. 

The  cycle  of  operation  of  the  gas  is  as  follows :  the  gas 
passes  from  the  compressor  into  a  cylinder  in  which  the  oil  from 
the  lubricator  of  the  cylinder  is  separated  from  the  gas.  From 
this  tank  the  gas  passes  to  the  condensing  coils  where  the  latent 
heat  is  taken  from  it  and  the  gas  as  it  becomes  a  liquid  flows  to  a 
receiving  tank,  being  carried  there  by  gravity. 

From  this  liquid  tank,  the  gas  is  conducted  through  piping  to 
the  freezing  coils,  where  it  is  liberated  from  the  condensing  pres- 
sure to  the  vaporizing  pressure,  usually  30  to  50  pounds  per  square 
inch.  A  far  greater  back  pressure  can  be  carried  than  with 
ammonia  when  accomplishing  the  same  work.  This  is  due  to 
the  much  lower  vaporizing  temperature,  (boiling  point)  of  the 
carbonic  anhydride  gas  in  a  liquefied  form  when  passing  from  a 
liquid  to  a  vapor  by  the  taking  up  of  latent  heat. 

Carbonic  Anhydride  gas  when  liquefied  to  be  used  as  a  re- 
frigerant may  be  applied  through  a  brine  tank,  cooling  the  brine 
which  afterwards  may  be  circulated  in  cooling  coils  in  refrigerator 
boxes  or  rooms.  This  system  is  known  as  the  indirect.  The 
process  of  sending  the  gas  direct  through  the  piping  suspended 
in  the  refrigerating  rooms  is  known  as  the  direct  application  of 
refrigerating  fluid. 

REFRIGERATION  BY  COMPRESSED  AIR. 

To  obtain  refrigeration  by  compressing  and  expanding  air,  we 
resort  to  the  effort  of  compression,  and  while  air  is  compressed 
conduct  off  the  heat  which  has  multiplied  in  proportion  to  the 
amount*  of  compression.  We  can  convert  the  heat  held  by  the 
air  into  power  ;  then  the  air  containing  but  little  heat  is  used  for 
refrigerating  purposes. 

That  this  may  be  more  clearly  understood  let  us  consider  the 
following  :  By  taking  air  at  atmospheric  pressure  at  sea  level, 
usually  14.7  pounds  per  square  inch  (this  varies  as  the  pressure 
increases  or  diminishes  as  shown  by  the  mercury  column  in  a 
barometer)  and  compressing  it  to  150  pounds  per  square  inch, 
ten  volumes  of  air  have  been  compressed  into  the  space  occupied 
by  one  volume  at  atmospheric  pressure.  The  heat  which  was 
contained  in  the  ten  volumes  has  been  forced  into  the  one  volume. 


KEFKIGERATION 


The  temperature  is  increased  because-  the  total  amount  of  heat 
is  now  in  the  one  volume.  The  increase  of  heat  is  in  proportion  to 
the  compression.  This  is  the  important  factor  which  makes  possi- 
ble refrigeration  by  mechanical  means. 


From  the  compressor,  the  air  is  discharged  into  piping  which 
is  surrounded  by  water  5  the  heat  is  thus  carried  off  and  the  tem- 
perature of  the  air  is  reduced  to  that  of  the  surrounding  water. 


KEFKIGEBATION  89 

Should  the  air  be  liberated  at  this  time  there  would  be  but  a  slight 
reduction  in  temperature,  probably  from  20  to  30  degrees  Fah- 
renheit. 

Expansion  of  Air.  From  the  cooling  coils,  the  air  passes 
to  an  expanding  cylinder  which  is  not  unlike  a  steam  engine  cylin- 
der. The  air  at  the  pressure  of  150  pounds  expands  and  drives  a 
piston  which  is  connected  to  the  driving  shaft  of  the  machine  and 
aids  in  the  compression  of  air.  The  amount  of  work  accomplished 
by  this  cylinder  is  in  proportion  to  the  heat  the  air  contains,  and 
this  heat  is  used  up  or  converted  into  power.  The  air  is  delivered 
into  the  cooling  pipes  for  ice-making  or  refrigeration  at  a  tem- 
perature of  from  40  to  65  degrees  below  zero,  the  final  condition 
depending  upon  the  efficiency  of  the  machinery. 

The  machinery  represented  by  the  accompanying  drawings 
and  descriptions  is  in  use  in  the  United  States  Navy  and  has  been 
adopted  as  standard. 

First.  Assembled  parts  of  the  machine.  This  can  best  be 
understood  by  reference  to  Fig.  50.  The  machine  is  known  as 
the  Allen  Dense  Air  Ice  Machine. 

In  Fig.  51  we  have  three  cylinders  with  slide  valves,  not 
unlike  a  steam  engine,  A  in  fact  representing  a  steam  cylinder, 
driving  the  air  compressor  B.  This  cylinder  is  operated  by  a 
single  D  valve  and  controlled  by  a  throttling  governor  or  by  any 
governor  adapted  to  conditions  at  sea.  Power  from  the  steam 
cylinder  is  conducted  by  connecting  rod  and  disc  crank,  to  which  is 
attached  a  driving  shaft  H  with  a  crank  in  the  center  of  the  shaft 
which  drives  the  air  compressor.  On  the  opposite  side  of  the 
shaft  is  a  disc  crank  from  which  the  expanding  cylinder  is  at- 
tached which  in  turn  aids  the  steam  cylinder  in  its  work.  F  is  a 
plunger  piston  pump  for  circulating  sea  water  around  the  coils 
in  the  cooling  tank  C.  G  is  a  priming  pump  for  air. 

In  the  location  of  cylinder  cranks,  the  crank  driving  the  air 
compressor  leads  the  steam  cylinder  about  30  degrees.  This  is 
the  practice  followed  by  the  best  engine  and  air  or  gas  compressor 
builders,  where  they  are  direct  connected.  The  object  of  the  lead 
is  to  apply  the  greatest  pressure  attainable  to  the  piston  of  the  air 
compressor  at  the  time  it  is  completing  its  stroke,  when  the  angle 
of  the  crank  pin  nears  the  position  exerting  the  greatest  effort  on 
the  crank  and  previous  to  the  time  of  the  closing  of  the  cut-off  on 
the  steam  cylinders.  By  this  method  a  much  lighter  fly  wheel 


90 


REFRIGERATION 


REFRIGERATION  91 ' 


can  be  used,  for  the  power  developed  by  the  engine  is  applied 
directly  through  the  shaft  and  not  transmitted  to  the  fly  wheel  to  be 
given  off  when  the  compression  of  the  air  cylinder  is  taking  the 
maximum  power  and  the  steam  crank  is  nearly  completing  its 
stroke. 

Air  Compressor  *«  B."  In  considering  the  action  of  this 
specially  designed  air  compressor,  we  find  that  the  suction  is  taken 
through  the  opening  in  the  bottom  of  the  valve  chest,  the  opening 
being  located  in  the  same  way  as  the  exhaust  on  a  slide  valve 
engine.  The  discharge  is  through  the  face  of  the  valve  chest, 
the  location  again  being  similar  to  the  steam  supply  to  a  slide-valve 
engine.  The  valves  are  of  the  slide  design.  It  is  a  question  with 
engineers  whether  or  not  this  design  is  superior  to  the  poppet 
valve  as  used  by  ammonia  and  kindred  gas  compressors.  The 
advantages  of  using  the  slide  valves  are :  first,  they  are  compara- 
tively noiseless ;  second,  they  are  not  constantly  hammering  their 
seats  or  faces  in  closing,  and  third, .  there  is  no  unbalanced  pres- 
sure of  the  valve  seat  to  be  overcome  by  the  engine,  or  to  cause 
the  rapid  destruction  of  the  metal  forming  a  poppet  valve. 

!N"ote :  For  a  description  of  unbalanced  valve  operation  see 
page  93. 

In  the  operation  of  the  valves  we  find  two  rocker  shafts,  each 
of  which  is  operated  by  an  eccentric  from  the  main  shaft.  The 
rocker  shaft  nearest  to. the  main  shaft  operates  the  valve  admitting 
steam  to  the  engine  A;  this  is  a  plain  D  valve.  The  shaft  also 
operates  the  rider  valve  on  both  air  compressor  and  expander 
cylinder. 

The  second  rocker  shaft  operates  the  main  valve  of  the  com- 
pressor and  the  expander  cylinder.  From  the  crosshead  of  the 
air  compressor  an  arm  extending  horizontally  operates  the  charg- 
ing air  pump  and  also  the  water  circulating  pump.  Water  from 
the  water  cooler  is  continuously  flowing  around  the  jacket  of  the 
air  compressing  cylinder.  The  action  of  the  expanding  chamber 
is  the  same  as  though  steam  were  used  to  move  the  piston,  the 
energy  given  by  this  expansion  of  air  aids  in  driving  the  air  com- 
pressor, thereby  adding  to  the  economy  of  the  operation.  This 
is  not,  however,  the  primary  cause  for  this  construction.  By  using 
the  air,  which  is  at  high  pressure,  to  obtain  power,  the  heat  that 
it  contains  is  consumed  or  converted  into  power  and  at  60  pounds 
per  square  inch,  which  is  the  back  pressure  carried,  there  is  ob- 


92 


EEFEIGEKATION 


REFRIGERATION 


93 


tained  a  temperature  of  from  70  to  90  degrees  below  zero.  This 
can  be  obtained  with  a  working  initial  pressure  of  260  pounds  per 
square  inch.  In  no  instance  is  the  latent  heat  of  the  air  affected 
except  to  a  slight  degree,  equaling  in  ratio  the  ability  of  the  air  to 
carry  latent  heat  due  to  the  different  specific  temperatures  during 
the  compression  and  expansion. 

Relief  of  Valves.  Should  the  pressure  in  the  expanding 
cylinder  become  greater  than  the  pressure  in  the  discharge  cham- 
ber, due  to  the  distortion  of  rods  or  slipping  of  eccentrics,  the 
valves  would  spring  back  from  their  seats  and  relieve  the  pressure. 
Upon  the  receding  of  the  piston  the  valve  would  close. 

Unbalanced  Valve  Pressure.  In  considering  this  question, 
let  us  take  a  poppet  valve  for  our  illustration;  this  is  shown  in 
Fig.  53. 

The  design  calls  for  a 
6-inch  compressing  cylinder 
with  a  valve  seat  of  f  inch 
face  giving  a  bearing  surface 
on  top  of  the  valve  6  J  inches 
in  diameter.  The  area  of  the 
cylinder  equals  28. 274  square 
inches,  while  the  area  of  the 
top  of  the  valves  including 
the  seat  is  33.183  square 
inches.  Let  us  consider  a 
working  pressure  of  150 
pounds  per  square  inch.  To 
open  this  valve  there  must  be 
exerted  a  pressure  of  150  x 
33.183  =  4977.45  pounds. 
The  power  exerted  on  the 
under  side  of  the  valve,  when 
the  pressures  are  equal  to  that 
of  the  discharge  chamber,  is 

28.274  x  150  =  4241.1  pounds,  or  in  order  to  open  the  valve  there 
must  be  added  4977.45 — 4241.1  =  636.35  pounds.  In  other  words, 
to  force  the  valve  from  its  seat  there  must  be  exerted  28.53  pounds 
per  square  inch  in  excess,  or  a  total  pressure  above  the  valve  of 
150+28.53=178.53  pounds  per  square  inch  on  the  entire  compress- 
ing piston.  This  power  is  overcome  by  placing  springs  or  com- 


FIG.  53 


94  REFEIGEBAtlON 


pressing  chambers  on  top  of  the  valve,  the  latter  by  far  the  most 
satisfactory. 

The  loss  caused  by  this  defect  in  design  of  poppet  valve  equals 
19.02  per  cent  of  the  entire  requirements  for  compression  of  gases. 

Oil  and  Water  Traps.  In  the  main  discharge  line  from  the 
air-expanding  cylinder  to  the  ice-making  tank,  is  placed  a  sepa- 
rator E,  for  intercepting  water  or  oil  that  may  be  in  the  system. 
The  water  is  carried  in  at  any  time  when  fresh  air  is  taken  to 
replenish  the  air  in  use  in  the  cycle  of  operation.  These  air-blows 
or  vents  are  used  upon  starting  up  a  refrigerating  plant.  The 
vents  in  the  cooling  chamber  C,  can  be  blown  off  at  any  time  but 
this  usually  occurs  at  the  starting  of  the  plant. 

The  very  low  temperature  of  the  air  congeals  any  water  or  oil 
that  may  remain  in  the  system ;  this  freezing  taking  place  in  the 
piping  or  oil  traps.  This  insures  dry  air  to  work  with.  The 
jacket  around  the  bottom  of  'the  trap  is  to  receive  steam  when  it  is 
desired  to  remove  the  oil  or  water,  the  latter  collecting  and  remain- 
ing in  the  separator  as  snow.  These  traps  hang  vertically  so  that 
the  operation  of  gathering  the  water  and  oil  is  one  of  gravity.  In 
the  plan  (Fig.  51)  they  are  shown  as  being  horizontal.  This  is 
never  done  in  practice  but  shows  more  clearly  the  arrangement  of 
different  parts. 

Ice  Making  Tank.  The  air  is  ejected  from  the  expanding 
cylinder,  and  after  passing  the  trap  enters  a  series  of  pipes  divided 
up  into  manifolds  and  coils  to  cause  the  air  to  travel:  many  times 
from  one  end  to  the  other,  to  form  a  long  coil.  It  is  not  necessary 
that  this  should  be  a  continuous  coil,  as  there  are  no  liquids  to 
vaporize.  The  air  takes  up  specific  heat  only  and  conveys  it.  back 
to  the  compressing  cylinder  for  removal  in  the  cooler  in  the  ex- 
panding cylinder. 

Surrounding  the  air  coils  in  the  ice  tank  is  a  solution  of  brine 
made  from  Chloride  of  Calcium.  The  ice  moulds  used  are  formed 
of  cans  made  of  galvanized  iron  the  same  as  those  used  for  ice 
making  plants.  The  condition  of  the  air  in  passing  from  the 
ice-making  tank  is  governed  by  the  quantity  of  ice  withdrawn. 
This  should  not  be  sufficient  to  raise  the  temperature  of  the  air 
above  zero  Fahr.  This  increases  the  amount  of  heat  taken  from 
the  tank  from  60  degrees  below  zero  to  zero,  or  about  two  British 
thermal  units  for  each  cubic  foot  of  air  passing  through  the  cycle. 


REFRIGERATION-  95 


Refrigerator  Box.  The  air  from  the  ice-making  tank  passes 
into  the  refrigerator  box  coils,  entering  at  a  temperature  of  zero. 
These  coils  are  made  with  a  manifold  at  each  end  with  divisions 
in  the  manifolds  to  direct  the  flow  of  air,  causing  a  circulation 
back  and  forth  of  three  times  the  length  of  the  box.  By  this 
method  of  distributing  the  circulation,  a  small  pipe  system  can 
be  used  for  the  piping,  while  the  headers  are  of  an  area  equaling 
the  discharge  from  the  expanding  cylinder.  The  required  area  for 
the  circulating  pipes  is  made  up  of  several  of  the  smaller  pipes. 
This  is  not  a  vital  or  even  a  necessary  point.  A  large  pipe  could 
be  erected,  giving  the  entire  area  of  the  exhaust  cylinder  opening. 
This  would  increase  the  friction  of  the  passage  of  air  over  the 
design  as  illustrated  in  the  plan. 

Water  ••  Butt  "  or  Cooler.  From  the  refrigerator  box,  the 
air  passes  through  a  coil  of  pipe  in  a  tank  filled  with  water.  The 
object  being  the  cooling  of  the  water  for  the  use  of  the  men.  This 
is  the  last  operation  of  the  air  and  it  is  desired  to  have  the  air  at  as 
high  a  temperature  as  is  consistent  with  the  work. 

The  application  of  compressed  air  was  first  made  successful  in 
ocean  steamships  carrying  meat  to  Europe.  The  engines  were  so 
large  that  no  auxiliary  boiler  could  furnish  sufficient  steam;  so 
that  to  cool  the  refrigerator  box  it  required  the  starting  of  one 
of  the  ship's  main  boilers.  The  air  was  exhausted  from  the  box 
at  atmospheric  pressure,  and  from  the  expanding  cylinder 
it  was  discharged  directly  into  the  refrigerator  box.  The  result 
was  that  tlie  oil  used  for  lubrication  became  very  strong  in  the 
air  and  left  a  taste  in  the  meat.  The  moisture  in  the  atmosphere 
was  turned  to  snow  as  it  came  in  contact  with  the  cool  air;  this 
snow  in  turn  becoming  melted  when  striking  the  sides  or  floor  of 
the  refrigerator  or  coming  in  contact  with  the  merchandise  in  ship- 
ment. This  has  been  remedied  by  enclosing  the  air  in  piping  and 
having  a  continuous  cycle  of  the  cooling  fluid  in  operation. 

In  no  instance  does  the  liquefaction  of  air  enter  into  the 
problem  of  refrigerating  with  air. 

In  the  work  of  construction,  iron  pipe  may  be  used,  with  any 
of  the  pipe  cements  for  joints  common  to  first  class  piping. 

The  following  instructions  for  starting  and  operating  tho 
Allen  Dense  Air  Tec  Machines  are  used  by  the  United  States  Navy. 

On  starting  the  machine,  have  the  blow  valves  of  the  expander 


96  EEFEIGEEATION 


and  the  pet-cocks  of  the  various  traps  open  until  no  more  grease 
or  water  discharges. 

The  two  IJ-inch  or  2-inch  valves  of  the  main  pipes  must  be 
open  and  the  1-inch  by-pass  pipe  closed;  also  the  J-inch  hot-air 
valves  from  the  compressor  to  the  expander  cylinder  must  be 
closed. 

Be  sure  that  the  circulating  water  is  in  motion. 

The  full  pressure  is  60  to  65  Ibs.  low  pressure,  and  210  to 
225  Ibs.  high  pressure. 

During  the  running,  open  the  pet-cocks  of  the  water-trap 
which  takes  the  water  out  of  the  air  from  the  primer  pump,  fre- 
quently enough  that  it  will  never  be  more  than  half  filled.  If  the 
water  should  be  allowed  to  enter  the  main  pipes,  it  is  liable  to 
freeze  and  clog  at  the  valves. 

By  keeping  all  stuffing  boxes  well  lubricated  by  the  lubricator 
cups,  the  pressures  are  easily  maintained  with  but  little  screwing 
up  of  the  packing. 

If  the  low-air  pressure  is  not  maintained,  the  fault  is  almost 
always  due  to  leaks  at  the  stuffing  boxes.  Under  all  circumstances 
it  is  due  to  some  leak  into  the  atmosphere,  as  we  have  never  yet 
found  the  primer  pump  valves  at  fault. 

The  packing  of  valve  stems  and  piston  rods  consists  of  a  few 
inner  rings  of  Katzenstein's  soft  metal  packing,  then  a  hollow 
greasing  ring,  then  soft  fibrous  packing  (Garlock  packing). 

The  sight  feed  lubricators  of  the  compressor  and  expander 
should  only  use  a  light  pure  mineral  machine  oil,  from  which  the 
paraffine  has  been  removed  by  freezing — usually  three  drops  per 
minute  in  the  compressor  and  one  or  two  in  the  expander. 

The  pistons  of  the  compressor  and  expander  cylinders  are 
packed  with  cup  leathers,  which  commonly  last  about  one  or  two 
months  of  steady  work.  When  these  leathers  give  out,  the  high 
pressure  decreases  in  relation  to  the  low  pressure,  and  the  ap- 
paratus shows  a  loss  of  cold.  A  leak  at  any  other  point  of  high 
pressure  into  low  pressure  will  have  the  same  effect. 

These  packing  leathers  are  made  of  thick  kip  leather,  or  of 
white  oak-tanned  leather  of  somewhat  less  than  -J-inch  thickness. 
They  are  cut  f  inch  larger  in  diameter  than  the  cylinders.  The 
leathers  must  be  kept  soaked  with  castor  oil  and  must  be  well 
soaked  in  that  before  using ;  and  a  tin  box  containing  spare  leathers 
and  castor  oil  must  be  kept  on  hand. 


REFRIGERATION  07 

Once,  or  sometimes  twice,  a  day,  it  is  necessary  to  clean  the 
machine  by  heating  it  np  and  blowing  ont  all  the  oil  and  ice 
deposits.  This  is  done  as  follows : 

The  1-inch  valve  of  the  by-pass  is  opened.  Then  the  two  1^ 
or  2-inch  valves  in  the  main  pipes  are  closed ;  then  the  two  ^-inch 
valves  in  the  hot  air  pipe  from  the  compressor  chest  to  the  expander 
are  opened,  and  the  l^-inch  valve  of  expander  inlet  is  closed 
partly;  then  the  live  steam  is  let  into  the  jacket  of  the  oil-trap 
slowly,  keeping  the  outlet  from  the  steam  jacket  open  enough  to 
drain  the  condensed  steam. 

Run  in  this  manner  for  about  one-half  hour,  during  this  time 
frequently  blow  out  the  bottom  valve  of  the  oil-trap,  also  the  blow- 
off  from  the  expander,  •  until  everything  appears  clean.  Then 
shut  off  the  steam  and  drain  connections  of  the  jacket  of  the  trap 
and  the  hot  air  pipe  from  the  compressor  to  the  expander.  Then 
open  the  two  1^ -inch  valves  in  main  pipes.  Then  close  the*  1-inch 
by-pass  pipe  and  all  pet-cocks  and  run  as  usual. 

Whenever  opportunity  offers  to  blow  out  the  manifolds  of 
the  meat-room  and  the  ice-making  box  (that  is,  whenever  they 
are  thawed),  this  should  be  done. 

If  it  is  suspected  that  a  considerable  quantity  of  oil  and  water 
have  got  into  the  pipe  system  and  are  clogging  the  areas  and  coat- 
ing the  surfaces,  the  pipes  can  be  cleaned  by  running  hot  air 
through  them  as  is  done  during  the  daily  cleaning  of  the  machine. 
The  oil  and  water  are  then  drawn  off  at  the  bottom  of  the  ice- 
making  box  and  the  manifolds  of  refrigerating  coils. 

The  clearance  of  the  two  air  pistons  and  of  the  primer  plunger 
is  only  -J  inch ;  therefore  not  much  change  of  piston  rods  and  con- 
necting rods  is  permissible,  and  when  the  piston  nuts  are  un- 
screwed to  change  the  piston  leathers,  the  rod  should  be  watched 
that  it  does  not  unscrew  from  the  crosshead. 

Whenever  it  is  noticed  that  the  brine  freezes,  more  chloride 
of  calcium  should  be  added  and  should  be  well  stirred  into  the 
brine. 

ABSORPTION  SYSTEM. 

By  the  rapid  vaporization  of  water  in  the  desert  of  Arabia, 
due  to  the  intensely  dry  atmosphere,  the  first  ice,  other  than  that 
formed  by  the  natural  process  of  winter  freezing,  was  made.  For 
cooling  large  quantities  of  water,  this  process  is  in  use  to-day  on 
a  more  clearly  defined  and  greatly  enlarged  plan  known  as  the 


98 


REFRIGERATION 


Water  Cooling  Tower.  This  method  is  being  extensively  used 
for  cooling  for  condensing  ammonia  gas  or  for  condensing  the  ex- 
haust steam  from  an  engine. 

Carre's  First  Ice  Plant:  From  the  use  of  this  system  of 
vaporization,  Carre,  a  French  scientist,  constructed  the  first  device 
for  cooling  by  mechanical  means  and  producing  ice,  and  all  devices 
for  absorption  refrigeration  owe  their  results  to  the  work  so  ably 
accomplished  by  him. 

A  definition  of  the  terms  used  in  the  two  systems  in  con- 
nection with  refrigerating  machinery  is  as  follows : 

Absorption  Refrigeration,  In  the  absorption,  as  in  the  com- 
pression system,  it  is  necessary  to  maintain  pressure  upon  the 

ammonia  gas  when  freed  from 
water  in  order  that  it  may 
become  liquefied,  and  during 
its  period  of  liquefaction 
give  up  the  latent  heat. 

The  Carre  original  ma- 
chine consisted  of  two  strong 
iron  jars  connected  together 
with  an  iron  pipe  as  shown  in 
Fig.  54.  In  the  jar  A,  or 
ammonia  still,  was  placed  a 
quantity  of  highly  charged  aqua  ammonia.  A  spirit  lamp  E  was 
placed  under  the  jar.  An  air  cock  was  placed  at  I,  and  when  the 
jar  became  heated,  the  air  cock  was  opened  until  the  air  was  ex- 
hausted. The  pressure  increased  in  both  jars  and  connection  A,  B, 
C.  Jar  C  was  placed  in  a  tank  and  surrounded  by  cold  water  D. 
The  supply  of  this  water  was  constantly  changing  so  that  at  all 
times  the  water  remained  cold  or  at  its  original  temperature,  which 
we  may  assume  at  60  degrees  Fahr.  The  heat  from  the  lamp 
caused  the  ammonia  to  vaporize  and  a  pressure  was  obtained  suffi- 
cient to  liquefy  the  gas  in  the  jar  C.  This  pressure  was  about  120 
pounds  per  square  inch.  The  intense  pressure  made  by  the  am- 
monia gas  was  sufficient  to  raise  the  boiling  pressure  of  the  water 
to  230  degrees  Fahr.,  thereby  preventing  the  vaporization  of  the 
water.  This  temperature  was  ample  to  drive  out  a  large  amount 
of  gas. 

After  the  process  was  complete,  which  was  determined  by 
the  length  of  time  that  the  heat  was  exposed  to  jar  A,  the  lamp 
was  removed.  The  water  was  drawn  off  from  around  jar  C  and 


Fig.  54. 


REFRIGERATION  99 


the  tank  filled  with  whatever  substance  it  was  desired  to  freeze. 
A  water  pipe  allowed  water  to  flow  over  the  jar  A  and  cool  its 
contents,  the  result  being  that  the  pressure  was  removed  from 
both  jars  A  and  C,  and  the  liquid  anhydrous  gas  began  to  vaporize 
in  jar  C,  the  gas  returned  to  jar  A,  and  was  taken  up  in  the  water 
from  which  it  had  been  expelled.  By  the  passage  of  the  anhydrous 
ammonia  from  a' liquid  into  a  gas,  the  heat  which  was  taken  up 
and  caused  the  vaporization,  being  held  latent  by  the  gas,  was 
taken  from  the  surrounding  liquid  in  tank  D. 

This  produced  a  low  temperature,  the  boiling  point  of  liquid 
anhydrous  ammonia  being  at  atmospheric  pressure  47  degrees  be- 
low zero  Fahr.  The  ratio  of  the  temperature  and  pressure  deter- 
mines the  temperature  at  which  the  gas  boils  in  passing  from  a 
liquid  to  a  gaseous  condition. 

Reabsorbing.  As  the  expanded  gases  return  to  the  jar  A  and 
come  in  contact  with  the  water,  they  are  absorbed  by  the  water  and 
in  this  process  of  absorption,  the  heat,  which  is  taken  up  latent  by 
vaporization  in  the  freezing  jar  C,  is  given  off.  The  heat  thus 
given  off  in  the  jar  A  is  carried  away  by  the  water  flowing  from 
connection  H. 

It  was  by  this  simple  device  that  Carre  established  the  princi- 
ples of  refrigeration.  We  should  remember  that  it  was  in  18 58 when 
this  work  was  done  and  that  the  methods  of  working  iron  were  then 
very  crude.  Carre's  success  was  due  to  his  patience  and  endurance. 

In  Fig.  55  is  shown  a  double  plant  absorption  machine,  in- 
cluding an  ice  making  tank,  each  machine  having  a  capacity  of 
12^  tons,  or  a  2 5 -ton  ice-making  output  for  every  twenty-four 
hours  of  constant  operation.  The  plants  are  connected  together  so 
that  they  can  be  interchangeable  in  their  working  parts. 

The  following  is  a  brief  description :  An  ammonia  still  A  is 
built  of  iron  pipe  12  inches  in  diameter  with  heavy  flanged  heads, 
which  are  of  wrought  iron,  screwed  on  to  the  pipe  and  soldered 
where  the  pipe  and  metal  of  the  head  joins.  The  object  of  a 
flanged  head  is  to  admit  of  coils  in  the  interior.  A  strong  solution 
of  aqua  ammonia  is  placed  in  the  still  and  heated  by  a  steam  spiral 
coil  placed  in  the  interior  of  the  still.  In  operation,  the  aqua  am- 
monia still  is  kept  about  one-third  filled  with  aqua  ammonia.  In 
naming  the  parts  of  the  apparatus,  each  designer  or  builder  selects 
names  to  suit  his  fancy.  While  the  part  used  for  applying  heat 
to  the  aqua  ammonia  is  necessary  to  all  designs  of  absorption 


100 


*     ' 


EEFEIGERATION 


QOOOOOO 
OC^OOOOCD  \- 

y.Q- 


KEFKIGEKATION  101 

machinery,  we  find  it  bearing  the  following  names:  '"ammonia 
boiler/7  "ammonia  still/'  "ammonia  pressure  generator." 

The  steam  connection  is  not  shown  in  the  drawing.  The  am- 
monia gas  is  driven  off  by  heat  and  passes  up  through  fhe^conjiec- 
tion  T  into  the  dehydrating  coil  B.  As  the  ammonia:  gai  passes 
from  the  sjill,it  carries  with  it  a  small  quantity  of  wa^e^in^ 
ing  condition  which  is  separated  from  the  gas  iri^lie 
coil.  This  coil  is  enclosed  in  a  tank  and  filled  with  water  which  is 
maintained  at  a  temperature  of  approximately  150  degrees  Fahr. 
At  this  temperature  the  water  condenses,  but  allows  the  ammonia 
to  remain  a  gas.  The  pressure  in  the  still  corresponds  to  the  tem- 
perature being  maintained  in  the  condenser  for  liquefaction.  Here 
the  same  ratio  is  obtained  as  in  the  compression  machines,  usually 
from  110  to  180  pounds  per  square  inch.  It  is  usually  considered 
necessary  to  maintain  150  pounds  per  square  inch  for  liquefaction. 
This  requires  condensing  water  at  approximately  60  degrees. 

From  the  dehydrating  coil  the  gas  and  water  pass  to  a  sepa- 
rate tank  C,  which  is  a  plain  cylinder.  The  action  is  to  separate 
the  gas  from  the  water,  the  gas  passing  from  the  top  of  the  sepa- 
rating tank  C  to  the  condenser  coil  D,  while  the  water  which  has 
been  separated  from  the  gas  by  the  action  of  the  dehydrating  coil 
drops  by  gravity  through  pipe  L  and  valves  10  back  to  the  still. 

The  law  of  gravity  holds  good  in  all  cases  and  under  all 
circumstances  where  pressures  are  the  same.  Therefore,  in  all 
parts  of  the  ammonia  generating  plant  this  law  of  falling  of  liquids 
'by  gravity  is  made  use  of  and  care  must  be  taken  in  designing 
plants  that  liquids  will  come  to  their  proper  places  by  gravity. 

The  ammonia  gas  is  now  separated  from  water  and  passes 
to  the  condenser  for  liquefying. 

Ammonia  Condensers.  The  condenser  coils  D  may  be  en- 
closed in  a  tank  and  surrounded  with  water,  or  they  may  be  left 
open  to  the  atmosphere  and  the  water  allowed  to  drip  over  them. 
In  the  ammonia  condenser,  the  heat  held  latent  by  the  ammonia 
gas  is  given  off  and  a  liquefaction  takes  place,  the  liquid  ammonia 
having  the  appearance  of  clear  water.  The  ammonia  drops  into 
a  liquid  storage  tank  E,  through  connection  P. 

Freezing  or  Ice  Making  Tank.  The  ammonia  is  now 
liquefied  and  ready  for  use  under  a  pressure  normally  of  150 
pounds  per  square  inch. 

Note:     Do  not  confuse  liquid  ammonia  with  anhydrous  ammonia. 


102 


BEFKIGEKATIOK 


Erom  the  liquid  tank  E,  the  liquid  ammonia  flows  through 
the  connecting  pipe  Q,  being  held  in  check  by  the  main  liquid 
valve  5.  The  object  of  this  main  liquid 
i»»  e* valve-  is  to  simplify  the  working  of  the 
<plant.v  Ttie:nme  valves  12,  are  the  ex- 
o "S «  ?;  padding: valves/ each  connected  to  the 
* v  coir  of  pipe  in  the  freezing  tank.  Each 
coil  has  a  separate  return  with  a  stop 
valve,  entering  connection  13.  The 
tank  is  shown  with  insulation  but  the 
coils  are  not  shown.  This  freezing  tank 
is  designed  to  hold  240  cans  or  ice 
moulds,  each  having  the  capacity  of  200 
pounds  of  ice,  when  the  freezing  is  com- 
plete. The  tank  is  eight  cans  wide  and 
thirty  cans  long,  or  a  tank  9  feet  wide 
by  60  feet  long  and  36  inches  deep,  in- 
side measure.  These  tanks  may  be 
built  either  of  iron  or  wood  as  the  de- 
signer wishes.  The  coils  run  the  entire 
length  of  the  tank,  between  the  cans  and 
outside  of  them. 

Freezing*  In  operating,  the  main 
liquid  valve  5  is  opened  and  the  gas 
flows  to  the  nine  expanding  valves  12, 
which  are  opened  to  permit  a  flow  of 
gas  through  an  opening  varying  from 
T^o"  to  J  of  a  square  inch. 

Low  Pressure  Side  of  the  Ap- 
paratus. At  this  point  the  gas  is  al- 
lowed to  pass  from  the  pressure  under 
which  it  is  condensed  to  the  vaporizing 
pressure,  usually  from  150  to  15 
pounds  per  square  inch. 


Note:  In  all  cases  where  pressures 
are  referred  to,  the  zero  point  is  the  at- 
mosphere and  not  absolute  zero. 


TO  STEAM 
TRAP 

Fig.  5(1. 


The  liquefied  ammonia  entering 
the  freezing  coils  under  pressure  of  15 
pounds  per  square  inch  immediately  begins  to  vaporize  and  in  so 


REFRIGERATION  103 


doing  takes  the  specific  heat  from  the  water.  The  heat  passes 
through  the  iron  pipes,  is  taken  up  and  returned  to  the  absorber  G 
through  connection  S.  The  boiling  point  of  liquid  ammonia  at  15 
pounds  pressure  approximates  26  degrees  below  zero  Fahr.  The 
action  of  the  ammonia  in  boiling  is  identical  to  water  boiling  at 
212  degrees  in  the  atmosphere,  with  which  every  one  is  familiar. 

Absorber.  The  vaporized  gas  flows  into  the  top  of  the  ab- 
sorber where  it  meets  the  water  from  which  the  gas  has  been 
driven. 

Circuit  of  Weak  Water.  Returning  now  to  the  ammonia 
still ;  during  the  period  of  distillation,  the  water,  freed  from  the 
gas  by  heat  and  called  by  different  names  such  as  "mother  liquid," 
"weak  water,"  etc.,  is  allowed  to  flow  from  the  bottom  of  the  still 
through  connection,  M,  and  passing  through  "heat  exchanger"  or 
"equalizer"  J,  flows  on  to  weak  water  cooler  V,  entering  the  cooling 
coil  at  the  bottom.  It  is  preferable  to  have  this  coil  enclosed  in  a 
tank  so  as  to  get  the  advantage  of  "Baudlett"  system  of  cooling  or 
the  bringing  of  the  hot  water  to  the  hot  gas  and  cold  water  to  the 
cold  gas.  From  this  cooler,  the  weak  liquid  returns  to  the  ab- 
sorber G,  through  valve  9.  The  water  is  carried  to  the  top  where 
it  falls  down  over  a  spiral  coil  of  water  pipes.  The  wrater  and 
gas  here  intermingle  and  the  water  absorbing  the  gas  is  allowed  to 
flow  into  reservoir  H.  A  strong  solution  of-  aqua  ammonia  is  taken 
by  the  pump  through  connection  8  and  returned  to  the  still  through 
connection  7,  there  to  be  re-distilled  and  the  cycle  of  operation 
again  to  be  performed. 

Pressure  Gages.  There  are  two  pressure  gages :  one  being  a 
high-pressure  and  the  other  a  low-pressure  instrument.  The  high- 
pressure  gage  reads  from  zero  to  300  pounds  or  more,  the  low- 
pressure  being  a  combination  gage  reading  from  30  inches  vacuum 
to  150  pounds  pressure  per  square  inch,  the  zero  point  being  at 
atmosphere  and  not  absolute.  These  gages  are  connected  as  fol- 
lows ;  the  high  pressure  gage  to  the  head  of  the  ammonia  still  A, 
the  low  pressure  gage  to  the  head  of  the  absorbing  tank  G.  Stop 
valves  must  be  placed  in  the  gage  lines  between  absorber  and  still- 
tank  heads  to  permit  the  removal  of  the  gages  for  cleaning  or 
repairs.  In  locating  gages,  a  position  about  12  inches  higher  than 
the  eyes  should  be  chosen.  At  this  point  they  are  easily  seen  and 
accessible  for  cleaning. 


104  REFKIGERATION 

A  steam  gage  is  required  on  the  steam  line  entering  the  still, 
also  a  reducing  valve  on  the  steam  line  to  control  the  pressure  of 
steam.  The  steam  gage  is-  connected  between  the  reducing  valve 
and  the  ammonia  still  steam  coil. 

A  steam  trap  is  placed  on  the  discharge  of  the  steam  coil 
coming  from  the  still,  and  so  connected  as  to  keep  the  still  coils 
free  from  water  at  all  times. 

Glass  Gages.  It  is  common  with  many  builders  of  refrig- 
erating and  ice-making  plants  to  place  on  their  systems  glass  gages, 
in  order  to  determine  the  amount  of  liquid  in  the  different  parts  by 
actual  observation.  Many  accidents  of  a  severe  nature  have  been 
the  result  of  breaking  these  glass  tubes. 

Automatic  Gage  Cocks.  There  have  been  many  devices  to 
close  the  gage  cocks  automatically  in  case  of  breaking  the  glass ; 
one  device  being  the  placing  of  long  lever  handles  on  the  plug 
cocks  and  closing  them  by  a  rope  over  a  pulley  at  a  safe  distance. 
These  glasses  are  often  made  36  inches  in  length,  and  from  that 
down  to  a  few  inches. 

Enclosed  Glass  Gages.  It  is  often  the  practice  to  enclose 
these  glass  tubes  within  a  pipe  split  for  a  quarter  of  an  inch  on 
opposite  sides  and  the  space  between  the  glass  and  the  tube  filled 
with  plaster  of  paris ;  or,  to  make  the  tubes  quite  thin  and  drill 
holes  through  them,  the  drill  passing  straight  from  side  to  side  and 
at  right  angles  to  the  pipe,  the  object  being  that  when  the  glass 
bursts  the  pipe  covering  keeps  the  glass  from  flying  and  injuring 
the  attendant. 

Glass  Gages  in  Operation.  It  is  a  fact  that  most  gages 
after  they  have  been  in  use  about  six  months  become  filled  with  a 
dirty  substance,  and  become  inoperative,  their  reading  being  mis- 
leading to  the  attendant.  To  the  successful  operation  of  any  re- 
frigerating plant,  either  compression  or  absorption,  the  presence 
of  glass  gages  is  an  unnecessary  adjunct,  and  the  attendant  soon 
becomes  so  familiar  with  his  plant  that  he  can  operate  it  without 
reference  to  glass  gages. 

In  installing  and  first  charging  a  plant,  these  gages  are  a 
convenience  but  not  a  necessity.  In  order  to  charge  a  plant  with- 
out gages,  the  engineer  must  know  positively  the  amount  of  liquid 
necessary  to  fill  the  different  parts  of  his  apparatus.  Often  ther- 
mometers are  inserted  to  determine  the  temperatures  of  the  liquids 


KEFKIGEKATION  105 

at  the  different  parts.  This  may  be  very  important  to  determine 
the  positive  condition  where  a  test  is  made  for  laboratory  purposes. 
In  the  parts  of  the  apparatus  shown  in  Fig.  55,  glass  gages 
could  be  located  on  ammonia  still  A  about  30  inches  from  the  bot- 
tom of  the  tank ;  a  glass  about  24  inches  long  should  be  used.  The 
water  collecting  at  this  point  should  fill  the  tank  to  a  height  of 
about  45  inches  from  the  bottom,  which  would  bring  it  to  the 
center  of  the  glass.  A  thermometer  could  also  be  inserted  in  the 
still  6  inches  from  the  bottom,  this  to  be  an  angle  thermome- 
ter and  a  "thimble"  inserted  to  come  in  contact  with  the  liquid. 
In  this  thimble  the  bulb  of  the  thermometer  should  be  p^ced. 
This  thermometer  should  read  from  80  to  300  degrees  Fahrenheit. 

Absorbing  Tank  Glass  Gages  and  Thermometer.  Glass 
gages  and  thermometer  may  be  placed  on  this  tank  in  the  same 
way  as  those  described  for  the  distilling  tank  A.  On  liquid  re- 
ceiving tank  E  glass  gages  may  be  placed,  the  connection  being 
made  in  the  head  or  from  the  upper  and  lower  sides  of  the  tank. 
This  glass  is  to  indicate  the  quantity  of  liquefied  ammonia  in  the 
tank. 

Operating  Without  Glass  Gages.  The  object  of  a  refrig- 
erating or  ice-making  plant  is  to  do  the  work  for  which  it  is 
designed,  and  when  an  absorption  plant  is  operating  and  the 
output  is  not  equal  to  the  amount  that  it  has  turned  out  when 
operating  at  its  best,  either  it  is  short  in  some  requirements  neces- 
sary to  make  it  work  successfully,  or  there  is  present  a  condition 
that  is  foreign  to  the  best  working  condition.  No  glass  gages  can 
determine  these  conditions  for  the  attendant.  Only  familiarity 
with  his  plant  will  instruct  him  what  to  do.  Passing  his  hand  on 
the  weak  water  pipe  as  it  leaves  the  still  and  also  on  the  return  for 
the  water  entering  the  absorber,  will  tell  him  the  conditions  neces- 
sary for  successful  operation. 

Gas  Foreign  to  Ammonia.  One  of  the  most  serious  ob- 
stacles to  the  successful  operation  of  absorption  ice-making  ma- 
chinery is  the  generating  with  the  ammonia  still  of  a  super- 
abundance of  free  hydrogen  gas,  ammonia  gas  being  composed  of 
three  parts  nitrogen  gas. 

There  is  present  in  the  still,  water  which  forms  the  method  of 
transit  of  the  ammonia  for  part  of  its  journey.  This  water  is 
formed  of  two  parts  of  hydrogen  to  one  part  of  oxygen.  The  iron 


106  REFRIGERATION 


piping  forming  the  heating  coils  has  a  large  capacity  for  taking 
oxygen  and  holding  it  in  the  shape  of  iron  scales  or  rust.  The 
action  of  the  ammonia  tends  to  free  this  rust  or  oxygen  scale  from 
the  piping  on  which  it  has  formed  and  as  a  result  a  large  deposit  of 
scale  forms  in  the  ammonia  still.  The  worst  feature  is  that  the 
affiliation  of  the  oxygen  and  iron  has  liberated  a  large  amount  of 
free  hydrogen  gas  which  finally  rises  to  the  highest  point  in  the 
system,  usually  in  the  condensers,  and  remains  there  where  the 
conditions  are  not  right  for  it  to  liquefy,  because  there  is  not 
enough  nitrogen  gas  to  combine  with  it  and  form  new  ammonia. 
It  is  necessary  to  get  this  hydrogen  gas  out  of  the  system.  This  is 
done  by  having  a  valve  at  a  convenient  place  and  occasionally 
blowing  it  off.  In  a  refrigerating  plant  in  operation  in  1904, 
which  was  built  to  do  refrigeration  equal  to  the  melting  of  12 
tons  of  ice  for  every  twenty-four  hours  of  operation,  the  actual  re- 
sult upon  a  careful  observation,  where  the  conditions  permitted 
a  knowledge  of  the  facts,  was  2.6  tons.  Part  of  the  defect  prob- 
ably might  have  been  due  to  a  depreciated  charge  of  ammonia  gas. 


INDEX 


A 

Page 

Absorption  system  of  refrigeration 97 

absorber 103 

ammonia  condensers '.  101 

automatic  gauge  cocks 104 

circuit  of  weak  water. . .' 103 

freezing ,. 102 

freezing  tank 101 

gas  foreign  to  ammonia , 105 

glass  gauges 104 

pressure  gauges 103 

reabsorbing 99 

Agents  of  refrigeration 5 

Ammonia , 5 

loss  of " '. 73 

Ammonia  condenser 35 

*  atmospheric 39 

double-pipe 45 

submerged " 37 

Ammonia  receiver 49 

Atmospheric  condenser 39 

B 

Beaume  scale . . 57 

Brine 56 

Brine  cooler 14 

Brine  systems 58 

Brine  tank : 9 

C 

Carbonic  acid 5 

Carbonic  anhydride  gas  refrigeration 81 

-Carre's  first  ice  plant 98 

Centigrade  scale 4 

Compressed  air 5 

Compressed  air  refrigeration ; 87 

air  compressor  "B" 91 

expansion  of  air •  •  •  • 89 

ice  making  tank " 94 

oil  and  water  traps 94 

refrigerator  box 95 


108  INDEX 


Compressed  air  refrigeration 

relief  of  valves 93 

unbalanced  valve  pressure 93 

water  butt  or  cooler 95 

Compressor 18 

erection  of . . 26 

losses 32 

lubrication _". 30 

piston '../...."..:.: 25 

stuffing  box 20 

valves 22 

water  jacket 29 

D 

Direct  expansion  refrigeration GO 

purging  and  pumping  out  connection 63 

Double-pipe  condenser 45 

E 

Evaporators 8 

F 

Fahrenheit  scale 4 

L 

Latent  heat,  definition  of 3 

Loss  of  ammonia 73 

O 

Oil  separator  or  interceptor 49 

R 

Reaumer  scale 4 

Refrigeration 

absorption  system 97 

by  ammonia 5 

by  carbonic  anhydride  gas 81 

by  compressed  air • 87 

compression  system 5 

unit  of "-  3 

Refrigeration  agents 5 

Refrigerating  plant 

ammonia  condenser 35 

ammonia  receiver " 49 

compressors 18 

direct  expansion '. 60 

evaporators 8 

oil  separator  or  interceptor .'.-  49 

operation  and  management  of 70 

pipes 50 


INDEX  109 


Pape 
Refrigerating  plant 

pressure  gauges 53 

proportion  between  parts  of 74 

testing  and  charging 67 

valves 53 

-  .       S 

Slotted  water  pipe , 44 

Specific  heat,  definition  of 3 

Submerged  condenser 37 

Sulphur  dioxide 5 

T 

Tables 

calcium  brine  solution 79 

chloride  or  sodium  brine 80 

gas  liquefied,  temperature  of 81 

saturated  ammonia,  properties  of 78 

thermometer  scales 77 

Thermometers 3 

Centigrade 4 

Fahrenheit . . . : 4 

Reaumer 4 

U 

Units  of  machines  or  plants 3 


i 


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